Abstract:

A system for further enhancing speed, i.e. improving throughput in a
SEM-type inspection apparatus is provided. An inspection apparatus for
inspecting a surface of a substrate produces a crossover from electrons
emitted from an electron beam source 25•1, then forms an image
under a desired magnification in the direction of a sample W to produce a
crossover. When the crossover is passed, electrons as noises are removed
from the crossover with an aperture, an adjustment is made so that the
crossover becomes a parallel electron beam to irradiate the substrate in
a desired sectional form. The electron beam is produced such that the
unevenness of illuminance is 10% or less. Electrons emitted from the
sample W are detected by a detector 25•11.

Claims:

1. An electron beam apparatus comprising:means for applying an electron
beam to a sample;means for macro-projecting electrons, which obtained
information of the surface of said sample with application of said
electron beam to said sample, to form an image on a detector; andmeans
for synthesizing as an image said electrons made to form an image on the
detector,wherein the shape of the irradiation area in which said electron
beam is applied to said sample is approximately symmetric with respect to
two axes orthogonal to the optical axis of said electron beam,the
illuminance of said electron beam in said irradiation area is
uniform,said means for applying an electron beam and said means for
forming an image are an optical system comprised of an electrostatic
lens,said means for synthesizing comprises means for multiplying said
electrons, means for converting said electrons multiplied by said
multiplying means into light, and a TDI-CCD converting light from said
means for converting electrons into light into electric signals for
images, andthe voltage of said electrostatic lens is adjusted to
determine a pixel size on the surface of said sample for obtaining a
desired magnification of macro-projection based on the pixel size of said
TDI-CCD.

2. An electron beam apparatus according to claim 1, further
comprising:means for guiding electrons, which obtained information of the
surface of said sample with application of the electron beam to said
sample, to a detector; andmeans for synthesizing said electrons guided to
the detector as an image,wherein the number of incident electrons
required for obtaining an image of maximum luminance is 1000/pixel.

3. The electron beam apparatus according to claim 2, wherein the line
frequency of said detector is 300 kHz to 1500 kHz, and said TDI-CCD has a
pixel number of 2048 to 4096, a tap number of 32 to 128, and a
sensitivity of 1000 DN/(nJ/cm2) to 40000 DN/(nJ/cm2).

4. The electron beam apparatus according to claim 1, wherein said
electrons are minor electrons reflected near the surface of said sample.

5. The electron beam apparatus according to claim 1, wherein the pixel
size of said TDI-CCD is equal to or smaller than a size that is twice as
large as the size of an inspection object so that the inspection object
existing on said sample can be found.

6. The electron beam apparatus according to claim 6, wherein the pixel
size of said TDI-CCD is a pixel size equal to or smaller than a value
obtained by magnifying a design rule by a factor.

7. The electron beam apparatus according to claim 6, wherein said design
rule shows a half pitch of wiring in the case where said sample is a
memory, and shows a gate length in the case where said sample is a logic.

8. An electron beam apparatus comprising:means for applying an electron
beam to a sample;means for macro-projecting electrons, which obtained
information of the surface of said sample with application of said
electron beam to said sample, to form an image on a detector; andmeans
for synthesizing as an image said electrons made to form an image on the
detector,wherein the illuminance of said electron beam in said
irradiation area is uniform,said means for forming an image is an optical
system comprised of an electrostatic lens,means for separating said
electron beam from said electrons is a deflector using an electric field
and a magnetic field,the center of the image formed by macro-projection
on said detector and the center of said electrostatic lens are on a
common axis, andin a section between said deflector and said sample, said
electron beam has said common axis as an optical axis, and said optical
axis of said electron beam is approximately perpendicular to said sample.

9. The electron beam apparatus according to claim 8, wherein said
electrons are mirror electrons reflected near the surface of said sample.

10. The electron beam apparatus according to claim 8, wherein said optical
system comprises two pairs of objective lenses, two pairs of intermediate
lenses and two pair of projection lenses, and reduces at least one of
chromatic aberration, a spherical aberration and a coma aberration
generated in relation to image formation.

11. The electron beam apparatus according to claim 8, wherein said
electrons are guided to said detector without being deflected by said
deflector.

12. The electron bean apparatus according to claim 8, wherein said
electrons are made to form an image at the center of said deflector by
said objective lens.

13. The electron beam apparatus according to claim 8, wherein energy when
said electron bean, is applied to said sample is controlled.

Description:

RELATED APPLICATION

[0001]This application is a divisional of U.S. application Ser. No.
12/073,892 filed on Mar. 11, 2008, which is a divisional of U.S.
application Ser. No. 11/378,465 filed on Mar. 20, 2006, now U.S. Pat. No.
7,365,724, which is a divisional application of U.S. application Ser. No.
10/754,623 filed Jan. 12, 2004, now U.S. Pat. No. 7,138,629, which is
hereby incorporated by reference in its entirety. Priority under 35
U.S.C. §§120 and 121 is hereby claimed for benefit of the
filing date of U.S. patent application Ser. Nos. 12/073,892, 11/378,465
and 10/754,623.

BACKGROUND OF THE INVENTION

[0002]1. Field of the Invention

[0003]The present invention relates to an inspection apparatus inspecting
defects or the like of a pattern formed on the surface of an inspection
object using an electron beam, and particularly relates to an inspection
apparatus irradiating an electron beam to the inspection object and
capturing secondary electrons modified according to properties of the
surface thereof to form image data, and inspecting in high throughput a
pattern or the like formed on the surface of the inspection object based
on the image data, and a device production process of producing a device
in a high yield using the inspection apparatus as used for detection of
wafer defects in semiconductor manufacturing. More specifically, the
present invention relates to a detection apparatus with a projection
electron microscope system using broad beams, and a device production
process using the apparatus.

[0004]In a semiconductor process, the design rule is about to move into an
era of 100 nm, and the type of production is now making a transition from
low variety and large production represented by DRAM to high variety and
small production found in SOC (Silicon on chip). Accordingly, the number
of production steps increases, improvement in yield for each step becomes
essential, and inspection of defects coming from the process becomes
important. The present invention relates to an apparatus for use in
inspection of a wafer or the like after each step in the semiconductor
process, and relates to an inspection process and apparatus using an
electron beam or a device production process using the same.

[0005]2. Description of the Related Art

[0006]As semiconductor devices is highly integrated, and patterns becomes
finer, a high resolution and high throughput inspection apparatus is
required. For inspecting defects of a wafer substrate having a 100 nm
design rule, pattern defects or defects of particle vias in wiring having
a line width of 100 nm or smaller and electric defects thereof should be
observed, and hence a resolution of 100 nm or lower is required, and the
inspection quantity increases due to an increase in the number of
production steps resulting from high integration of the device, and
therefore high throughput is required. Furthermore, as the device is
increasingly multilayered, the inspection apparatus is required to have a
function of detecting a contact failure (electric defects) of vias for
connection of wiring between layers. Currently, optical defect inspection
apparatuses are mainly used, but defect inspection apparatuses using
electron beams are expected to go mainstream in stead of the optical
defect inspection apparatus in terms of resolution and inspection of
contact failure. However, the electron beam-type defect inspection
apparatus has a disadvantage, i.e. it is inferior in throughput to the
optical type.

[0007]Thus, development of an inspection apparatus having a high
resolution and high throughput and being capable of detecting electric
detects is required. It is said that the resolution of the optical type
is maximum 1/2 of the wavelength of light used, which is equivalent to
about 0.2 μm for commercially practical visible light, for example.

[0008]On the other hand, for the type using an electron beam, a scanning
electron beam type (SEM type) is usually commercially available, the
resolution is 0.1 μm and the inspection time is 8 hours/wafer (200 mm
wafer). The electron beam type has a remarkable characteristic such that
electric defects (breakage of wiring, poor conduction, poor conduction of
vias and the like) can be inspected, but the inspection speed is very
low, and development of a defect inspection apparatus performing
inspection at a high speed is expected.

[0009]Generally, the inspection apparatus is expensive, inferior in
throughput to other process apparatuses, and is therefore used after an
important step, for example, etching, film formation, or CMP (chemical
mechanical polishing) planarization processing under present
circumstances.

[0010]The inspection apparatus of the scanning type using an electron beam
(SEM) will be described. The SEM type inspection apparatus reduces the
size of an electron beam (the beam diameter corresponds to the
resolution), and scans the beam to irradiate a sample in a line form. On
the other hand, a stage is moved in a direction perpendicular to the
scanning direction of the electron beam to irradiate an observation area
with the electron beam in a plain form. The scan width of the electron
beam is generally several hundreds μm. Secondary electrons generated
from the sample by irradiation with the size-reduced electron beam
(refereed to as primary electron beam) are detected with a detector
(scintillator+photomultiplier (photomultiplier tube) or a
semiconductor-type detector (PIN diode type) or the like). Coordinates of
the irradiation position and the amount of secondary electrons (signal
intensity) are synthesized into an image, and the image is stored in a
storage device, or outputted onto a CRT (cathode ray tube). The principle
of the SEM (scanning electron microscope) has been described above, and
defects of a semiconductor (usually Si) wafer in a step on progress are
detected from the image obtained by this process. The inspection speed
(corresponding to throughput) depends on the amount of primary electron
beams (current value), the beam diameter and the response speed of the
detector. 0.1 μm of beam diameter (that can be considered as
resolution), 100 nA of current value and 100 MHz of detector response
speed are maximum values at present and in this case, it is said that the
inspection speed is about 8 hours per wafer having a diameter of 20 cm.
The serious problem is that this inspection speed is very low compared to
the optical type ( 1/20 or less of that of the optical type).
Particularly, pattern defects and electric defects of a device pattern of
a design rule of 100 nm or smaller formed on the wafer, i.e. of a line
width of 100 nm, a via with the diameter of 100 nm or smaller and the
like, and a contaminant of 100 nm or smaller can be detected at a high
speed.

[0011]For the SEM-type inspection apparatus described above, the above
inspection speed is considered as a limit, and a new type of inspection
apparatus is required for further enhancing the speed, i.e. increasing
the throughput.

SUMMARY OF THE INVENTION

[0012]For meeting the needs, the present invention provides an electron
beam apparatus comprising means for irradiating an electron beam to a
sample, means for guiding to a detector electrons obtaining information
about the surface of the above described sample by the irradiation of the
electron beam to the above described sample, and means for synthesizing
as an image the electrons being guided to the detector and obtaining
information about the surface of the above described sample,

[0013]wherein the illuminance of the above described electron beam in an
area of the above described sample illuminated with the above described
electron beam is uniform.

[0014]The electrons obtaining information about the surface of the above
described sample are desirably at least one of secondary electrons,
reflection electrons and back-scatter electrons, or mirror electrons
reflected from the vicinity of the surface of the above described sample.

[0015]By the inspection process or inspection apparatus of the present
invention, defects of a substrate of a wafer or the like having wiring
with the line width of 100 nm or smaller can be inspected.

[0017]FIG. 2 shows the overall configuration of the apparatus of FIG. 1;

[0018]FIG. 3 shows the overall configuration of the apparatus of FIG. 1 in
terms of functions;

[0019]FIG. 4 shows main components of an inspection unit of the apparatus
of FIG. 1;

[0020]FIG. 5 shows main components of the inspection unit of the apparatus
of FIG. 1;

[0021]FIG. 6 shows main components of the inspection unit of the apparatus
of FIG. 1;

[0022]FIG. 7 shows main components of the inspection unit of the apparatus
of FIG. 1;

[0023]FIG. 8 shows main components of the inspection unit of the apparatus
of FIG. 1;

[0024]FIG. 9 shows main components of the inspection unit of the apparatus
of FIG. 1;

[0025]FIG. 10 shows main components of the inspection unit of the
apparatus of FIG. 1;

[0026]FIG. 11 shows a jacket of the apparatus of FIG. 1;

[0027]FIG. 12 shows the jacket of the apparatus of FIG. 1;

[0028]FIG. 13 is an elevational view showing main components of the
semiconductor inspection apparatus according to the present invention;

[0029]FIG. 14 is a front view showing main components of the semiconductor
inspection apparatus according to the present invention;

[0030]FIG. 15 shows one example of the configuration of a cassette holder
of the semiconductor inspection apparatus according to the present
invention;

[0031]FIG. 16 shows the configuration of a mini-environment apparatus of
the semiconductor inspection apparatus according to the present
invention;

[0032]FIG. 17 shows the configuration of a loader housing of the
semiconductor inspection apparatus according to the present invention;

[0033]FIG. 18 shows the configuration of the loader housing of the
semiconductor inspection apparatus according to the present invention;

[0034]FIGS. 19(A) and 19(B) illustrate an electrostatic chuck for use in
the semiconductor inspection apparatus according to the present
invention;

[0035]FIG. 20 illustrates the electrostatic chuck for use in the
semiconductor inspection apparatus according to the present invention;

[0036]FIGS. 20-1(A) and 21-1(B) illustrate another example of the
electrostatic chuck for use in the semiconductor inspection apparatus
according to the present invention;

[0037]FIG. 21 illustrates a bridge tool for use in the semiconductor
inspection apparatus according to the present invention;

[0038]FIG. 22 illustrates another example of the bridge tool for use in
the semiconductor inspection apparatus according to the present
invention;

[0039]FIG. 22-1 illustrates the configuration and operation procedures (A)
to (C) of an elevator mechanism in a load lock chamber of FIG. 22;

[0040]FIG. 22-2 illustrates the configuration and operation procedures (D)
to (F) of the elevator mechanism in a load lock chamber of FIG. 22;

[0041]FIG. 23 shows an alteration example of a method of supporting a main
housing in the semiconductor inspection apparatus according to the
present invention;

[0042]FIG. 24 shows an alteration example of the method of supporting a
main housing in the semiconductor inspection apparatus according to the
present invention;

[0043]FIG. 25-1 shows the configuration of an electro-optic system of a
projection electron microscope type beam inspection apparatus of the
semiconductor inspection apparatus according to the present invention;

[0044]FIG. 25-2 shows the configuration of the electro-optic system of the
scanning electron beam inspection apparatus of the semiconductor
inspection apparatus according to the present invention;

[0045]FIG. 25-3 schematically shows one example of the configuration of a
detector rotation mechanism of the semiconductor inspection apparatus
according to the present invention;

[0046]FIG. 25-4 schematically shows one example of the configuration of
the detector rotation mechanism of the semiconductor inspection apparatus
according to the present invention;

[0047]FIG. 25-5 schematically shows one example of the configuration of
the detector rotation mechanism of the semiconductor inspection apparatus
according to the present invention;

[0048]FIG. 26 is the first embodiment of the semiconductor inspection
apparatus according to the present invention;

[0049]Diagrams (1) to (5) of FIG. 27-1 each illustrate a shape of a sample
irradiating beam;

[0050]Diagrams (1-1) to (4) of FIG. 27-2 each illustrate an irradiation
form of a linear beam;

[0051]FIG. 28 illustrates secondary electrons being taking out from a
column in the semiconductor inspection apparatus according to the present
invention;

[0052]FIG. 29 shows the second embodiment of the semiconductor inspection
apparatus according to the present invention;

[0053]FIG. 30 shows the third embodiment of the semiconductor inspection
apparatus according to the present invention;

[0054]FIG. 31 shows the fourth embodiment of the semiconductor inspection
apparatus according to the present invention;

[0055]FIG. 32 shows the fifth embodiment of the semiconductor inspection
apparatus according to the present invention;

[0056]FIG. 33 illustrates an irradiation area covering an observation
area;

[0057]FIG. 34 illustrates the irradiation form and irradiation efficiency;

[0058]FIG. 35 shows the sixth embodiment of the semiconductor inspection
apparatus according to the present invention, and shows the configuration
of a detection system using a relay lens;

[0059]FIG. 36 shows the sixth embodiment of the semiconductor inspection
apparatus according to the present invention, and shows the configuration
of a detection system using an FOP;

[0060]FIGS. 37(A) and 37(B) show the eighth embodiment of the
semiconductor inspection apparatus according to the present invention;

[0061]FIG. 38 is a graph showing dependency of the transmittance on the
diameter of an opening;

[0062]FIG. 39 shows a specific example of an electron detection system in
the apparatus of FIG. 37;

[0063]FIGS. 40(A) and (B) illustrate requirements for operating the
electron detection system in the apparatus of FIG. 37 in three modes;

[0064]FIG. 41 shows the configuration of an E×B unit of the
semiconductor inspection apparatus according to the present invention;

[0065]FIG. 42 is a sectional view along the line A of FIG. 41;

[0066]FIG. 43 shows the ninth embodiment of the semiconductor inspection
apparatus according to the present invention;

[0067]FIG. 44 shows simulation of an electric field distribution;

[0068]FIG. 45 shows the configuration of a power supply unit of the
semiconductor inspection apparatus according to the present invention;

[0069]FIG. 46 shows a circuit system generating a direct-current voltage
in the power supply unit shown in FIG. 45;

[0070]FIG. 47 shows one example of the circuit configuration of a static
bipolar power supply of the power supply unit shown in FIG. 45;

[0071]FIG. 48 shows a special power supply in the power supply unit shown
in FIG. 45;

[0072]FIG. 49 shows a special power supply in the power supply unit shown
in FIG. 45;

[0073]FIG. 50 shows a special power supply in the power supply unit shown
in FIG. 45;

[0074]FIG. 51 shows one example of a power supply circuit for a retarding
chuck in the power supply unit shown in FIG. 45;

[0075]FIG. 52 shows one example of the hardware configuration of an EO
correcting deflection voltage in the power supply unit shown in FIG. 45;

[0076]FIG. 53 shows one example of the circuit configuration of an
octupole conversion unit in the power supply unit shown in FIG. 45;

[0077]FIG. 54(A) shows one example of the circuit configuration of a
high-speed and high-voltage amplifier in the power supply unit shown in
FIG. 45, and FIG. 54(B) shows an output waveform;

[0078]FIG. 55 shows the first embodiment of a precharge unit of the
semiconductor inspection apparatus shown in FIG. 13;

[0079]FIG. 56 shows the second embodiment of a precharge unit of the
semiconductor inspection apparatus shown in FIG. 13;

[0080]FIG. 57 shows the third embodiment of a precharge unit of the
semiconductor inspection apparatus shown in FIG. 13;

[0081]FIG. 58 shows the fourth embodiment of a precharge unit of the
semiconductor inspection apparatus shown in FIG. 13;

[0084]FIG. 61 shows another example of configuration of a defect
inspection apparatus comprising the precharge unit;

[0085]FIG. 62 shows an apparatus for converting a secondary electron image
signal into an electric signal in the apparatus shown in FIG. 61;

[0086]FIG. 63 is a flow chart illustrating the operation of the apparatus
shown in FIG. 61;

[0087]FIGS. 64(a), 64(b) and 64(c) show a method for detecting defects in
the flow chart of FIG. 63;

[0088]FIG. 65 shows another example of configuration of the defect
inspection apparatus comprising the precharge unit;

[0089]FIG. 66 shows still another example of configuration of the defect
inspection apparatus comprising the precharge unit;

[0090]FIG. 67 illustrates the operation of a control system of the
semiconductor inspection apparatus according to the present invention;

[0091]FIG. 68 illustrates the operation of the control system of the
semiconductor inspection apparatus according to the present invention;

[0092]FIG. 69 illustrates the operation of the control system of the
semiconductor inspection apparatus according to the present invention;

[0093]FIG. 70 illustrates the operation of the control system of the
semiconductor inspection apparatus according to the present invention;

[0094]FIG. 71 illustrates the operation of the control system of the
semiconductor inspection apparatus according to the present invention;

[0095]FIG. 72 illustrates the operation of the control system of the
semiconductor inspection apparatus according to the present invention;

[0096]FIG. 73 illustrates the operation of the control system of the
semiconductor inspection apparatus according to the present invention;

[0097]FIG. 74 illustrates an alignment procedure in the semiconductor
inspection apparatus according to the present invention;

[0098]FIG. 75 illustrates the alignment procedure in the semiconductor
inspection apparatus according to the present invention;

[0099]FIG. 76 illustrates the alignment procedure in the semiconductor
inspection apparatus according to the present invention;

[0100]FIG. 77 illustrates a defect inspection procedure in the
semiconductor inspection apparatus according to the present invention;

[0101]FIG. 78 illustrates the defect inspection procedure in the
semiconductor inspection apparatus according to the present invention;

[0102]FIG. 79 illustrates the defect inspection procedure in the
semiconductor inspection apparatus according to the present invention;

[0103]FIGS. 80(A) and 80(B) illustrate the defect inspection procedure in
the semiconductor inspection apparatus according to the present
invention;

[0104]FIG. 81 illustrates the defect inspection procedure in the
semiconductor inspection apparatus according to the present invention;

[0105]FIG. 82 illustrates the defect inspection procedure in the
semiconductor inspection apparatus according to the present invention;

[0106]FIG. 83 illustrates the defect inspection procedure in the
semiconductor inspection apparatus according to the present invention;

[0107]FIG. 84 illustrates the configuration of the control system in the
semiconductor inspection apparatus according to the present invention;

[0108]FIG. 85 illustrates the configuration of a user interface in the
semiconductor inspection apparatus according to the present invention;

[0109]FIG. 86 illustrates the configuration of a user interface in the
semiconductor inspection apparatus according to the present invention;

[0110]FIG. 87 illustrates another function and configuration of the
semiconductor inspection apparatus according to the present invention;

[0111]FIG. 88 shows an electrode in another function and configuration of
the semiconductor inspection apparatus according to the present
invention;

[0112]FIG. 89 shows the electrode in another function and configuration of
the semiconductor inspection apparatus according to the present
invention;

[0113]FIG. 90 is a graph showing a voltage distribution between the wafer
and an objective lens;

[0114]FIG. 91 is a flow chart illustrating the secondary electron
detection operation in another function and configuration of the
semiconductor inspection apparatus according to the present invention;

[0273]First, the overall configuration of the semiconductor inspection
apparatus will be described.

[0274]The overall configuration of the apparatus will be described using
FIG. 1. The apparatus is comprised of an inspection apparatus main body,
a power supply rack, a control rack, an image processing unit, a film
formation apparatus, an etching apparatus and the like. A roughing vacuum
pump such as a dry pump is placed outside a clean room. The main part of
the interior of the inspection apparatus main body is comprised of an
electron beam optical column, a vacuum transportation system, a main
housing containing a stage, a vibration removal table, a turbo-molecular
pump and the like as shown in FIG. 2.

[0275]A control system comprises two CRTs and an instruction input feature
(keyboard or the like). FIG. 3 shows a configuration from a viewpoint of
a function. The electron beam column is mainly comprised of an
electro-optical system, detection system, an optical microscope and the
like. The electro-optical system is comprised of a lens and the like, and
a transportation system is comprised of a vacuum transportation robot, an
atmospheric transportation robot, a cassette loader, various kinds of
position sensors and the like.

[0276]Here, the film formation apparatus and etching apparatus, and a
cleaning apparatus (not shown) are placed side by side near the
inspection apparatus main body, but they may be incorporated in the
inspection apparatus main body. They are used, for example, for
inhibiting the charge of a sample or cleaning the surface of the sample.
If a sputtering system is used, one apparatus may have functions of both
film formation and etching apparatuses.

[0277]Although not shown in the figures, associated apparatuses may be
placed side by side near the inspection apparatus main body, or may be
incorporated in the inspection apparatus main body depending on the
purpose of use. Alternatively, the inspection apparatus may be
incorporated in the associated apparatus. For example, a
chemical-mechanical polishing apparatus (CMP) and the cleaning apparatus
may be incorporated in the inspection apparatus main body, or a CVD
(chemical vapor deposition) apparatus may be incorporated in the
inspection apparatus and in this case, there are advantages that the
installation area and the number of units for transportation of samples
can be reduced, and transportation time can be shortened, and so on.

[0278]Similarly, the film formation apparatus such as a plating apparatus
may be incorporated in the inspection apparatus main body. Similarly, the
inspection apparatus may be used in conjunction with a lithography
apparatus.

1-1) Main Chamber, Stage, Jacket of Vacuum Transportation System

[0279]In FIGS. 4, 5 and 6, main components of an inspection unit of the
semiconductor inspection apparatus are shown. The inspection unit of the
semiconductor inspection apparatus comprises an active vibration removal
table 4•1 for shutting off vibration from the outside environment,
a main chamber 4•2 as an inspection chamber, an electro-optical
apparatus 4•3 placed on the main chamber, an XY stage 5•1 for
scanning the wafer placed in the main chamber, a laser interference
measurement system 5•2 for control of the motions of the XY stage,
and a vacuum transportation system 4•4 accompanying the main
chamber, and they are placed in positional relations shown in FIGS. 4 and
5. The inspection unit of the semiconductor inspection apparatus further
comprises a jacket 6•1 for allowing environmental control and
maintenance of the inspection unit, and is placed in positional relations
shown in FIG. 6.

1-1-1) Active Vibration Removal Table

[0280]The active vibration removal table 4•1 has a weld platen
5•4 mounted on an active vibration removal unit 5•3, and the
main chamber 4•2 as an inspection chamber, the electro-optical
apparatus 4•3 placed on the main chamber, the vacuum transportation
system 4•4 accompanying the main chamber and the like are held on
the weld platen. In this way, vibrations in the inspection unit from the
external environment can be inhibited. In this embodiment, the natural
frequency is within ±25% of 5 Hz in the X direction, 5 Hz in the Y
direction and 7.6 Hz in the Z direction, and the control performance is
such that the transmission level of each axis is 0 dB or smaller at 1 Hz,
-6.4 dB or smaller at 7.6 Hz, -8.6 dB or smaller at 10 Hz and -17.9 dB or
smaller at 20 Hz (all under no load on the platen). In another structure
of the active vibration removal table, the main chamber, the
electro-optical apparatus and the like are suspended to be held. In still
another structure, stone platen is mounted to hold the main chamber and
the like.

1-1-2) Main Chamber

[0281]The main chamber 4•2 directly holds a turbo-molecular pump
7•2 in the lower part to achieve a certain degree of vacuum
(10-4 Pa or lower) in the inspection environment, and comprises
therein a high accuracy XY stage 5•1 for scanning the wafer, so
that a magnetic force from outside can be blocked. In this embodiment,
the following structure is provided to improve the flatness of the
holding surface of the high accuracy XY stage wherever possible. A lower
plate 7•3 of the main chamber is placed and fixed on an especially
high flatness area 7•4 (flatness of 5 μm or less in this
embodiment) prepared on the weld platen. Further, a middle plate is
provided as a stage holding surface in the main chamber. The middle plate
is supported at three points against the lower plate of the main chamber,
so that it is not directly affected by the flatness of the lower plate.
In this embodiment, a support part consists of a spherical seat
7•6. The middle plate is capable of achieving a flatness of the
stage holding surface at 5 μm or less when loaded with the self-weight
and the weight of the stage. Furthermore, to alleviate the effect of
deformation of the main chamber by a change in internal pressure (from
atmospheric pressure to reduced pressure of 10-4 Pa or lower) on the
stage holding surface, the middle plate is fixed directly on the weld
platen at near the three points at which the middle plate is supported on
the lower plate.

[0282]To accurately control the XY stage, a measurement system with a
laser interferometer at a stage position is installed. An interferometer
8•1 is placed under vacuum to inhibit a measurement error, and is
fixed directly on a high-rigidity chamber wall 7•7 in this
embodiment to reduce vibrations of the interferometer causing directly a
measurement error as small as 0. Furthermore, to eliminate errors of the
measurement position and the inspection position, the extended line of
the measurement area by the interferometer matches the inspection area as
accurately as possible. Furthermore, a motor 8•2 for XY motions of
the stage is held by the chamber wall 7•7 in this embodiment, but
if it is necessary that the effect of motor vibrations on the main
chamber is further inhibited, the motor 8•2 is held by the weld
platen 7•1 directly, and mounted on the main chamber in a structure
not transferring vibrations of a bellow and the like.

[0283]The main chamber 4•2 is composed of a material having a high
magnetic permeability to block the effect of an external magnetic field
on the inspection area. In this embodiment, the main chamber 4•2
has permalloy and iron such as SS 400 plated with Ni as an anticorrosive
coating. In another embodiment, permendur, super permalloy,
electromagnetic soft iron, pure iron or the like is used. Further, it is
effective to cover the periphery of the inspection area in the chamber
directly with a material having a high magnetic permeability as a
magnetic shielding effect.

1-1-3) XY Stage

[0284]The XY stage 5•1 can scan the wafer with high accuracy under
vacuum. Strokes of X and Y are each 200 to 300 mm for the 200 mm wafer,
and 300 to 600 mm for the 300 mm wafer. In this embodiment, the XY stage
is driven by the motor 8•2 for driving X and Y axes fixed on the
main chamber wall, and a ball screw 8•5 attached thereto via a
magnetic fluid seal 8•3. In this embodiment, since the XY motions
can be performed in a state in which the ball screw for driving X and Y
is fixed to the chamber wall, the stage structure is as follows.

[0285]First, in the lower stage, an Y stage 7•10 is placed, and a
ball screw 7•8 for driving and a cross roller guide 7•11 are
installed. On the Y stage, a middle stage 7•12 having thereon a
ball screw 7•14 for driving the X axis is placed, and an X stage
7•13 is mounted thereon. The middle stage and the Y stage and x
stage are connected together along the Y axis by the cross roller guide.
In this way, when the Y axis is shifted, the X stage is moved by the Y
stage and the connection area 7•14, and the middle stage remains
fixed. Another embodiment has a two-stage structure in which the middle
stage is aligned with the upper stage axis. Furthermore, in the XY stage
of another embodiment, the XY stage itself is driven by a linear motor.
Further, a high-accuracy mirror 8•4 (the flatness is λ/20 or
less, and the material is aluminum-deposited synthetic quartz) is
installed so that measurements can be made over the entire stroke by the
interferometer.

[0286]Furthermore, a θ stage 7•15 is placed on the XY stage
for performing wafer alignment under vacuum. In the θ stage in this
embodiment, two ultrasonic motors are placed for driving, and a linear
scale is placed for position control. Various cables connected to movable
parts performing X, Y and θ motions are clamped by cable bears each
held on the X stage and the Y stage, and connected to the outside of the
main chamber via a field-through provided on the chamber wall.

[0287]Specifications of this embodiment with the above structures are
shown in Tables 1 and 2.

[0288]The laser interference measurement system is comprised of a laser
optical system having an optical axis which is parallel to X and Y axes
and has an inspection position on its extended line, and an
interferometer 8•1 placed therebetween. The optical system in this
embodiment is placed in positional relations shown in FIGS. 9 and 10.
Laser light emitted from a laser 9•1 placed on the weld platen is
erected upright by a bender 9•2, and then bent to be parallel with
a measurement plane by a bender 10•1. Further, the laser light is
split into light for X axis measurement and light for Y axis measurement
by a splitter 9•4, then bent to be parallel with the Y axis and the
X axis by a bender 10•3 and a bender 9•6, respectively, and
guided into the main chamber.

[0289]An adjustment method in starting the optical system will be
described below. First, an adjustment is made so that laser light emitted
from the laser is bent perpendicularly by the bender 9•2, and bent
horizontally by the bender 10•1. Then, the bender 10•3 is
adjusted so that an optical axis of light bent by the bender 10•3
and reflected by a mirror 8•4 placed accurately perpendicularly to
the Y axis and returned perfectly matches an optical axis of incident
light. By making an observation of the optical axis just behind the laser
with the interferometer removed so as not to interrupt reflected light,
an accurate adjustment can be made. Furthermore, the optical axis
adjustment of the X axis can be performed independently with the splitter
9•4 and the bender 9•6 after performing the optical axis
adjustment of the Y axis. The adjustment can be performed as that of the
Y axis. Further, after the axes of incident light and reflected light of
the X axis and the Y axis are adjusted, the intersection point of the
optical axes (assuming that no mirror exists) should be made to match the
wafer inspection position. As a result, a bracket fixing the bender
10•3 can move perpendicularly to the Y axis, and a bracket fixing
the bender 9•6 can move perpendicularly to the X axis with incident
light and reflected light perfectly matching each other. Further, the
bender 10•1, the splitter 9•4, the bender 10•3 and the
bender 9•6 can desirably move vertically while retaining their
respective positional relations.

[0290]Furthermore, a method for adjustment of optical axes associated with
replacement of the laser in the apparatus in operation after initiation
will be described below. In the apparatus in operation in which the
inside of the main chamber is kept under vacuum, the optical axis or the
like having an interferometer removed has a difficulty. Thus, a tool for
placing targets 10•2 at several points on an optical path outside
the main chamber so that the optical path in the start can be assessed
only outside the main chamber is prepared. After replacement of the
laser, the adjustment made in the start can be reproduced by adjusting
the optical axis with respect to the target 10•2 only with an
adjustment feature provided on a laser mounting seat.

1-3) Inspection Unit Jacket

[0291]An inspection unit jacket 4•7 can be provided with a feature
as a flame structure for maintenance. In this embodiment, a containable
twin crane 11•1 is, provided on the upper part. The crane
11•1 is mounted on a traverse rail 11•2, and the traverse
rail is placed on a traveling rail (longitudinal) 11•3. The
traveling rail is usually housed as shown in FIG. 11, during maintenance,
the traveling rail rises as shown in FIG. 12, so that the stroke in the
vertical direction of the crane can be increased. Consequently, an
electro-optical apparatus 4•3, a main chamber top plate and the XY
stage 5•1 can be attached to/detached from the back face of the
apparatus by the crane included in the jacket during maintenance. Another
embodiment of the crane included in the jacket has a crane structure
having a rotatable open-sided axis.

[0292]Furthermore, the inspection unit jacket can also have a function as
an environment chamber. This has an effect of magnetic shielding along
with control of temperature and humidity as required.

2. EMBODIMENTS

[0293]Preferred embodiments of the present invention will be described
below as a semiconductor inspection apparatus inspecting a substrate,
i.e. a wafer having a pattern formed on the surface as an inspection
object, with reference to the drawings.

2-1) Transportation System

[0294]FIGS. 13 and 14 show main components of the semiconductor inspection
apparatus according to the present invention with an elevational view and
a front view. This semiconductor inspection apparatus 13•1
comprises a cassette holder 13•2 holding cassettes each containing
a plurality of wafers, a mini-environment apparatus 13•3, a loader
housing 13•5 constituting a working chamber, a loader 13•7
loading the wafer from the cassette holder 13•2 to a stage
apparatus 13•6 placed in a main housing 13•4, and an
electro-optical apparatus 13•8 placed in a vacuum housing, and they
are placed in positional relations shown in FIGS. 13 and 14.

[0295]The semiconductor inspection apparatus 13•1 further comprises
a precharge unit 13•9 placed in the vacuum main housing 13•4,
a potential application mechanism applying a potential to the wafer, an
electron beam calibration mechanism, and an optical microscope
13•11 constituting an alignment control apparatus 13•10 for
positioning the wafer on the stage apparatus.

2-1-1) Cassette Holder

[0296]The cassette holder 13•2 holds a plurality of cassettes
13•12 (two cassettes in this embodiment) (e.g. closed cassettes
such as SMIF and FOUP manufactured by Assist Co. Ltd.) each containing a
plurality of wafers (e.g. 25 wafers) housed with arranged vertically in
parallel. The cassette holder 13•2 may be freely selected and
placed such that if cassettes are conveyed by a robot or the like and
automatically loaded into the cassette holder 13•2, the cassette
holder 13•2 having a structure suitable for this arrangement is
selected, and if cassettes are manually loaded, the cassette holder
having an open cassette structure suitable for this arrangement is
selected. In this embodiment, the cassette holder 13•2 has a form
in which the cassettes 13•12 are automatically loaded, and for
example, a lift table 13•13, and a lift mechanism 13•14
vertically moving the lift table 13•13, wherein the cassette
13•12 can be automatically set on the lift table 13•13 in a
state shown by a chain line in FIG. 14, and after the cassette
13•12 is set, it is automatically rotated to a state shown by a
solid line in FIG. 14, and directed to a rotation axis line of a first
transportation unit in the mini-environment apparatus.

[0297]Furthermore, the lift table 13•13 is descended to a state
shown by a chain line in FIG. 13. In this way, a cassette holder having a
well known structure may be used as appropriate for any of the cassette
holder to be used when the cassette is automatically loaded and the
cassette holder when the cassette is manually loaded, and detailed
descriptions of their structures and functions are not presented.

[0298]In another embodiment, as shown in FIG. 15, a plurality of 300 mm
substrates are housed in a trench pocket (not described) fixed in a box
main body 15•1, and are conveyed, stored and so on. A substrate
transportation box 15•2 is comprised of the prismatic box main body
15•1, a substrate loading/unloading door 15•3 communicating
with a substrate loading/unloading door automatic opening/closing
apparatus so that an opening on the side face of the box main body
15•1 can be mechanically opened and closed, a lid 15•4
located opposite to the opening and covering openings for attachment and
detachment of filters and a fan motor, the trench pocket (not shown) for
holding a substrate W (FIG. 13), an ULPA filter 15•5, a chemical
filter 15•6 and a fan motor 15•7. In this embodiment,
substrates are loaded/unloaded by a robot-type first transportation unit
15•7 of the loader 13•7.

[0299]Furthermore, the substrate or wafer housed in the cassette
13•12 is to be inspected, and such inspection is performed after or
during a process of processing the wafer during the semiconductor
production step. Specifically, the substrate or wafer undergoing a film
formation step, CMP, ion implantation and the like, the wafer having a
wiring pattern formed on the surface, or the wafer having no wiring
pattern yet formed on the surface is housed in the cassette. For the
wafer housed in the cassette 12•12, a large number of wafers are
spaced vertically and arranged in parallel, and therefore an arm of the
first transportation unit can be moved vertically so that they can be
held by the wafer at any position and the first transportation unit
described later. Furthermore, the cassette is provided with a feature for
controlling a moisture content in the cassette to prevent oxidization and
the like of the wafer surface after the process. For example, a
dehumidifying agent such as silica gel is placed in the cassette. In this
case, any dehumidifying agent having an effect of dehumidification may be
used.

2-1-2) Mini-Environment Apparatus

[0300]In FIGS. 13 to 16, the mini-environment apparatus 13•3
comprises a housing 16•2 constituting a mini-environment space
16•1 arranged for undergoing control of the atmosphere, a gas
circulating apparatus 16•3 for circulating a gas such as cleaning
air in the mini-environment space 16•1 to control the atmosphere, a
discharge apparatus 16•4 collecting and discharging part of air
supplied into the mini-environment space 16•1, and a pre-aligner
16•5 placed in the mini-environment space 16•1 to roughly
position the substrate or wafer as an inspection object.

[0301]The housing 16•2 has a top wall 16•6, a bottom wall
16•7 and a circumference wall 16•8 surrounding the
circumference, and isolates the mini-environment space 16•1 from
outside. To atmosphere-control the mini-environment space 16•1, the
gas circulating apparatus 16•3 comprises a gas supply unit
16•9 mounted on the top wall 16•6 to clean a gas (air in this
embodiment) and flow the clean air just downward in a laminar form
through one or more gas blowout holes (not shown) in the mini-environment
space 16•1, a collection duct 16•10 placed on the bottom wall
16•7 to collect air flowed away toward the bottom in the
mini-environment space 16•1, a conduit 16•11 connecting the
collection duct 16•10 and the gas supply unit 16•9 to return
the collected air back to the gas supply unit 16•9, as shown in
FIG. 16.

[0302]In this embodiment, the gas supply unit 16•9 introduces about
20% of air to be supplied from outside the housing 16•2 and
cleaning the air, but the ratio of the gas introduced from outside can be
arbitrarily selected. The gas supply unit 16•9 comprises an HEPA or
ULPA filter having a well known structure for producing clean air. The
downward laminar flow, namely down flow, is principally supplied in such
a manner as to flow through the transportation plane by the first
transportation unit placed in the mini-environment space 16•1,
described later, to prevent deposition of pasty dust occurring from the
transportation unit on the wafer. Thus, a blast nozzle of the down flow
is not necessarily located near the top wall as shown in the figure, but
may be at any location on the upper side of the transportation plane by
the transportation unit. Furthermore, it is not required to flow the gas
throughout the mini-environment space 16•1.

[0303]Furthermore, in some cases, ion air can be used as clean air to
ensure cleanness. Furthermore, a sensor for observing the cleanness may
be provided in the mini-environment space 16•1, and the apparatus
may be shut down when the cleanness drops.

[0304]An entrance 13•15 is formed in an area adjacent to the
cassette holder 13•2 in the circumference wall 16•8 of the
housing 16•2. A shutter apparatus having a well known structure may
be provided near the entrance 13•15 to close the entrance
13•15 from the mini-environment apparatus side. The laminar down
flow produced near the wafer may flow at a flow rate of 0.3 to 0.4 m/sec.
The gas supply unit 16•9 may be provided outside the
mini-environment space 16•1, instead of being provided inside the
mini-environment space 16•1.

[0305]The discharge apparatus 16•4 comprises a suction duct
16•12 placed in the lower part of the transportation unit at a
location on the lower side of the wafer transportation plane of the
transportation unit, a blower 16•13 placed outside the housing
16•2 and a conduit 16•14 connecting the suction duct
16•12 and the blower 16•13. This discharge apparatus
16•4 suctions a gas flowing downward along the circumference of the
transportation unit and containing dust that may occur from the
transportation unit with the suction duct 16•12, and discharges the
gas to outside the housing 16•2 through the conduit 16•14 and
the blower 16•13. In this case, the gas may be discharged into a
discharge pipe (not shown) placed near the housing 16•2.

[0306]The pre-aligner 16•5 placed in the mini-environment space
16•1 optically or mechanically detects an orientation flat (flat
portion formed on the outer edge of a circular wafer, which is
hereinafter referred to as ori-fla) formed on the wafer, and one or more
V-type cutouts or notches formed on the outer edge of the wafer to
predefine the position of the wafer in the direction of rotation about
the axial line O-O with accuracy within about ±1°. The
pre-aligner 16•5 constitutes part of a mechanism determining the
coordinates of an inspection object, and plays a role to roughly position
the inspection object. The pre-aligner 16•5 itself may have a well
known structure, and thus the structure and operation thereof are not
presented.

[0307]Furthermore, although not shown in the figure, a collection duct for
discharge apparatus may be provided also in the lower part of the
pre-aligner 16•5 to discharge air containing dust discharged from
the pre-aligner 16•5 to outside.

2-1-3) Main Housing

[0308]In FIGS. 13 to 15, the main housing 13•4 constituting the
working chamber 13•16 comprises a housing main body 13•17,
and the housing main body 13•17 is supported by a housing
supporting apparatus 13•20 placed on a vibration blocking apparatus
or anti-vibration apparatus 13•19 placed on a base frame
13•18. The housing supporting apparatus 13•20 comprises a
frame structure 13•21 assembled in a rectangular form. The housing
main body 13•17 is fixedly placed on the frame structure
13•21, comprises a bottom wall 13•22 placed on the frame
structure, a top wall 13•23, and a circumference wall 13•24
connected to the bottom wall 13•22 and the top wall 13•23 to
surround the circumference, and isolates the working chamber 13•16
from outside. In this embodiment, the bottom wall 13•22 is made of
relatively thick steel plate so that the bottom wall 13•22 is not
deformed by the weight of equipment such as the stage apparatus and the
like placed above, but other structure may be adopted.

[0309]In this embodiment, the housing main body and the housing supporting
apparatus 13•20 are made to have a rigid structure, and the
anti-vibration apparatus 13•19 prevents transfer of vibrations to
this rigid structure from a floor on which the base frame 13•18 is
placed. An entrance 14•1 for loading/unloading the wafer is formed
on an area of the circumference wall 13•24 of the housing main body
13•17 adjacent to a loader housing described later.

[0310]Furthermore, the anti-vibration apparatus 13•19 may be an
active type having a pneumatic spring, magnetic bearing or the like, or
may be a passive type having the same. In any case, the apparatus may
have a well known structure, and therefore the structure and function of
the apparatus itself are not described here. The working chamber
13•16 is kept in a vacuum atmosphere by a vacuum apparatus (not
shown) having a well known structure. A control apparatus 2 for
controlling the operation of the overall apparatus is placed below the
base frame 13•18. The pressure of the main housing is usually at
10-4 to 10-6 Pa.

2-1-4) Loader Housing

[0311]In FIGS. 13 to 15 and FIG. 17, the loader housing 13•5
comprises a housing main body 14•4 constituting a first loading
chamber 14•2 and a second loading chamber 14•3. The housing
main body 14•4 has a bottom wall 17•1, a top wall 17•2,
a circumference wall 17•3 surrounding the circumference, and a
partition wall 14•5 partitioning the first loading chamber
14•2 and the second loading chamber 14•3, and can isolate
both the loading chambers from outside. The partition wall 14•5 is
provided with an opening or entrance 17•4 to give and take the
wafer between the loading chambers. Furthermore, entrances 14•6 and
14•7 are formed in areas of the circumference wall 17•3
adjacent to the mini-environment apparatus and the main housing.

[0312]The housing main body 14•4 of the loader housing 13•5 is
placed and supported on a frame structure 13•21 of the housing
supporting apparatus 13•20. Thus, transfer of vibrations of the
floor to the loader housing 13•5 is also prevented. The entrance
14•6 of the loader housing 13•5 is matched with an entrance
13•25 of the housing 16•2 of the mini-environment apparatus
13•3, and there a shutter apparatus 14•8 selectively
inhibiting communication between the mini-environment space 16•1
and the first loading chamber 14•2 is provided.

[0313]The shutter apparatus 14•8 has a seal material 13•26
surrounding the periphery of entrances 13•25 and 14•6 and
fixed in close contact with a side wall 17•3, a door 13•27
inhibiting passage of air through the entrance in cooperation with the
seal material 13•26, and a drive apparatus 13•28 driving the
door. Furthermore, the entrance 14•7 of the loader housing
13•5 is matched with the entrance 14•1 of the housing main
body 13•17, and there a shutter apparatus 13•29 selectively
seal-inhibiting communication between the second loading chamber
14•3 and the working chamber 13•16 is provided. The shutter
apparatus 13•29 has a seal material 13•30 surrounding the
periphery of entrances 14•7 and 14•1 and fixed in close
contact with side walls 17•3 and 13•24, a door 14•9
inhibiting passage of air through the entrance in cooperation with the
seal material 13•30, and a drive apparatus 13•31 driving the
door.

[0314]Further, an opening formed in the partition wall 14•5 is
provided with a shutter apparatus 14•10 selectively seal-inhibiting
communication between first and second loading chambers by closing the
opening with the door. The shutter apparatuses 14•8, 13•29
and 414•10 can air-tightly seal the chambers when they are in a
closed state. These shutter apparatuses may be well known shutter
apparatuses, and therefore detailed descriptions of the structures and
functions thereof are not presented.

[0315]Furthermore, a method of supporting the housing 16•2 of the
mini-environment apparatus 13•3 is different from a method of
supporting the loader housing, and to prevent vibrations from the floor
from being transferred through the mini-environment apparatus 13•3
to the loader housing 13•5 and the main housing 13•4, a
cushion material for prevention of vibrations may be so situated as to
air-tightly surround the periphery of the entrance between the housing
16•2 and the loader housing 13•5.

[0316]In the first loading chamber 14•2 is provided a wafer rack
14•11 supporting a plurality of wafers (two wafers in this
embodiment) in a horizontal state with the plurality of wafers spaced
vertically. As shown in FIG. 18, the wafer rack 14•11 has poles
18•2 mutually spaced and fixed upright at four corners of the
rectangular substrate 18•1, two-stage support portions 18•3
and 18•4 are formed on each pole 18•2, and the periphery of
the wafer W is borne on the support portion to hold the wafer. The
leading ends of the arms of first and second transportation units
described later are brought close to the wafer from between adjacent
poles to hold the wafer by the arms.

[0317]Loading chambers 14•2 and 14•3 can be
atmosphere-controlled to be in a high vacuum state (degree of vacuum is
10-4 to 10-6 Pa) by a vacuum pumping apparatus (not shown)
having a well known structure including a vacuum pump (not shown). In
this case, the first loading chamber 14•2 is kept in low vacuum
atmosphere as a low vacuum chamber, and the second loading chamber
14•3 is kept in a high vacuum atmosphere as a high vacuum chamber,
thus making it possible to effectively prevent contamination of the
wafer. By employing this structure, the wafer which is housed in the
loading chamber and is to be inspected for defects next can be conveyed
into the working chamber without delay. By employing this loading
chamber, together with the principle of a multi-beam electron apparatus
described later, the throughput of defect inspection can be improved, and
the degree of vacuum of the periphery of an electron source required to
be stored under high vacuum conditions can be kept at as high as
possible.

[0318]First and second loading chambers 14•2 and 14•3 are each
connected to an evacuation pipe and a vent pipe for inert gas (e.g. dry
pure nitrogen) (not shown). Consequently, the atmospheric pressure state
in each loading chamber is achieved with inert gas ventilation
(introducing an inert gas to prevent deposition on the surface of gases
such as oxygen gas other than the inert gas). The apparatus itself for
inert gas ventilation may have a well known structure, and therefore
detailed descriptions thereof are not presented.

[0319]Furthermore, in the inspection apparatus of the present invention
using an electron beam, it is important that such a material as,
typically, lantern hexaboride (LaB6) used for an electron
source of an electro-optical system described later is prevented as much
as possible from contacting oxygen and the like in order to prolong the
life of the electron source, when the material is heated to such a high
temperature that thermal electrons are emitted. This can be more reliably
accomplished by performing the atmosphere control described above in the
pre-stage where the wafer is loaded into the working chamber in which the
electro-optical system is placed.

2-1-5) Loader

[0320]The loader 13•7 comprises a robot-type first transportation
unit 16•14 placed in the housing 16•2 of the mini-environment
apparatus 13•3, and a robot-type second transportation unit
14•12 placed in the second loading chamber 14•3.

[0321]The first transportation unit 16•14 has a multi-nodular arm
16•16 capable of rotating about an axial line O1-O1 with
respect to a drive unit 16•15. The multi-nodular arm may have any
structure, but in this embodiment, it has mutually rotatably attached
three parts.

[0322]One part of the arm 16•16 of the first transportation unit
16•14, namely a first part closest to the drive unit 16•15 is
attached to a shaft 16•17 capable of rotating by a drive mechanism
(not shown) having a well known structure, provided in the drive unit
16•15. The arm 16•16 can rotate about an axial line
O1-O1 by the shaft 16•17, and can expand and contract in
the radial direction with respect to the axial line O1-O1 as a
whole by relative rotation among parts. A holding apparatus 14•13
holding the wafer such as a mechanical chuck or electrostatic chuck
having a well known structure is provided at the leading end of a third
part remotest from the shaft 16•17 of the arm 16•16. The
drive unit 16•15 can be moved vertically by a lift mechanism
16•18 having a well known structure.

[0323]In this first transportation unit 16•14, the arm 16•16
extends in a direction M1 or M2 of one of two cassettes held in the
cassette holder, and a wafer housed in the cassette is placed on the arm
or held by a chuck (not shown) mounted on the arm at the end to take out
the wafer. Thereafter, the arm contracts (into a state shown in FIG. 14),
rotates to a position in which the arm can extend in a direction M3 of
the pre-aligner 16•5, and stops at the position. Then, the arm
extends again and places the wafer held by the arm on the pre-aligner
16•5. The arm receives the wafer from the pre-aligner 16•5 in
the opposite manner, then further rotates and stops at a position in
which the arm can extend toward the second loading chamber 14•2 (in
direction M4), and places the wafer on a wafer seat in the second loading
chamber 14•2. Furthermore, if the wafer is mechanically held, the
wafer is held at its periphery (range of about 5 mm from the edge). This
is because a device (circuit wiring) is formed on the entire wafer except
for the periphery, and holding this area may cause destruction and
failure of the device.

[0324]The second transportation unit 14•12 has a structure
essentially identical to that of the first transportation unit, and the
only different point is that transportation of the wafer is carried out
between the wafer rack and the holding surface of the stage apparatus,
and detailed descriptions thereof are not presented.

[0325]In the loader 13•7 described above, first and second
transportation units 16•14 and 14•12 convey the wafer from
the cassette held in the cassette holder onto the stage apparatus
13•6 placed in the working chamber 13•16 and transport the
wafer in the opposite manner in almost a horizontal state, and the arm of
the transportation unit moves vertically only when the wafer is taken
from and inserted into the cassette, the wafer is placed onto and taken
from the wafer rack, and the wafer is placed onto and taken from the
stage apparatus. Thus, large wafer, for example, wafer having a diameter
of 300 mm can be moved smoothly.

[0326]Since the stage has a mechanism applying a backward bias to the
wafer, the arm is made to have a potential identical or close to that of
the stage or a floating potential when the arm is placing the wafer onto
the stage or taking the wafer from the stage, whereby a trouble such as a
discharge due to potential short is avoided.

2-1-6) Stage Apparatus

[0327]The stage apparatus 13•16 comprises a fixed table 13•32
placed on the bottom wall 13•22 of the main housing 13•4, a Y
table 13•33 moving in the Y direction (direction perpendicular to
the sheet plane in FIG. 1) on the fixed table, an X table 13•34
moving in the X direction (lateral direction in FIG. 1) on the Y table, a
rotation table 13•35 capable of rotating on the X table, and a
holder 13•36 placed on the rotation table 13•35. The wafer is
held on a wafer holding surface 14•14 of the holder 13•36 in
a releasable manner. The holder 13•36 may have a well known
structure capable of holding in a releasable manner the wafer
mechanically or in an electrostatic chuck mode. The stage apparatus
13•6 uses a servo motor, and encoder and various kinds of sensors
(not shown) to operate the plurality of tables described above, whereby
the wafer held by the holder on the holding surface 14•14 can be
positioned in the X direction, Y direction and Z direction (vertical
direction in FIG. 13) with respect to an electron beam emitted from the
electro-optical apparatus, and in the direction of rotation about an
axial line vertical to the wafer supporting surface (θ direction)
with high accuracy.

[0328]Furthermore, for positioning in the Z direction, for example, the
position of the holding surface on the holder may be fine-adjusted in the
Z direction. In this case, a reference position of the holding surface is
detected by a position measurement apparatus (laser interference distance
measuring apparatus using the principle of the interferometer) using a
laser having a very small diameter, and the position is controlled by a
feedback circuit (not shown), and/or the notch of the wafer or the
position of the oriental-flat is measured to detect a plane position or
rotation position of the wafer with respect to the electron beam, and a
rotation table is rotated by a stepping motor or the like capable of
performing control at a very small angle to control the position.

[0329]For preventing occurrence of dust in the working chamber wherever
possible, servo motors 14•15 and 14•16 and encoders
14•17 and 14•18 for stage apparatus are placed outside the
main housing 13•4. Furthermore, the stage apparatus 13•6 may
have a well known structure, which is used in, for example, a stepper,
and therefore detailed descriptions of the structure and operation are
not presented. Furthermore, the laser interference distance measuring
apparatus described above may have a well known structure, and therefore
detailed descriptions of the structure and operation are not presented.

[0330]An obtained signal can be normalized by previously inputting the
rotational position and X and Y positions of the wafer with respect to
the electron beam to a signal detection system or image processing system
described later. Further, a wafer chuck mechanism provided in the holder
gives a voltage for chucking the wafer to an electrode of an
electrostatic chuck, and holds three points (preferably equally spaced
along the circumference) on the outer edge of the wafer to perform
positioning. The wafer chuck mechanism comprises two fixed positioning
pins, and one pressing clamp pin. The clamp pin can realize automatic
chucking and automatic releasing, and comprises a conduction area for
application of a voltage.

[0331]Furthermore, in this embodiment, the table moving in the lateral
direction is the X table, and the table moving in the vertical direction
is the Y table in FIG. 14, but the table moving in the lateral direction
may be the Y table, and the table moving in the vertical direction may be
the X table in this figure.

2-1-7) Wafer Chucking Mechanism

2-1-7-1) Basic Structure of Electrostatic Chuck

[0332]For matching the focus of the electro-optical system with the sample
surface correctly and quickly, irregularities on the sample surface or
wafer surface are preferably as small as possible. Thus, the wafer is
adsorbed to the surface of an electrostatic chuck fabricated with high
flatness (preferably flatness of 5 μm or less).

[0333]Electrode structures of the electrostatic chuck include a unipole
type and a dipole type. The unipole type is a process in which conduction
is previously established on the wafer, and a high voltage (generally
about several tens to hundreds V) is applied to between the wafer and one
electrostatic chuck electrode to adsorb the wafer, while in the dipole
type, it is not necessary to force the wafer into conduction, and the
wafer can be adsorbed simply by applying positive and negative voltages
to two electrostatic chucks, respectively. Generally, however, to obtain
stable adsorption conditions, two electrodes should be formed into an
intricate shape like comb teeth, and thus the shape of the electrode
becomes complicated.

[0334]On the other hand, for inspection of the sample, a predetermined
voltage (retarding voltage) should be applied to the wafer in order to
obtain conditions for image forming for the electro-optical system or
ensure the state of the sample surface that can be easily observed with
electrons. It is necessary that this retarding voltage should be applied
to the wafer, and that the electrostatic chuck should be the unipole type
described above to stabilize the potential of the wafer surface.
(However, as described later, the electrostatic chuck should be made to
function as a dipole type until conduction with the wafer is established
with a conduction needle. Thus, the electrostatic chuck has a structure
capable of switching between the unipole type and the dipole type).

[0335]Thus, it is required to mechanically contact the wafer to force the
wafer into conduction. However, the need for prevention of contamination
of the wafer has intensified, and it is required to avoid mechanical
contact with the wafer, and there are cases where contact with the edge
of the wafer is not acceptable. In this case, conduction must be
established on the back face of the wafer.

[0336]On the back face of the wafer, a silicon oxide film is usually
formed, and it is impossible to establish conduction in this state. Thus,
needles are made to contact the back face of the wafer at two or more
locations, and a voltage is applied to between the needles, whereby the
oxide film can be locally destructed to establish conduction with silicon
as a wafer base material. The voltage applied to the needles is a DC
voltage or AC voltage of several hundreds V. Furthermore, the material of
the needle should be nonmagnetic, and have abrasion-resistance and a high
melting point, and tungsten or the like can be considered as such a
material. Furthermore, to impart durability or prevent contamination of
the wafer, it is effective to coat the surface with TiN or diamond.
Furthermore, to ensure that conduction with the wafer has been
established, it is effective to apply a voltage to between the needles to
measure a current.

[0337]It is the chucking mechanism shown in FIG. 19 that has been
fabricated in view of the background described above. The electrostatic
chuck is provided with electrodes 19•1 and 19•2 that
desirably have an intricate shape like comb teeth to adsorb the wafer W
with stability, three pusher pins 19•3 for giving and taking the
wafer, and two or more conduction needles 19•4 for applying a
voltage to the wafer. Furthermore, a correction ring 19•5 and a
wafer dropping mechanism 19•6 are placed around the electrostatic
chuck.

[0338]The pusher pin 19•3 already protrudes from the electrostatic
chuck surface when the wafer W is conveyed by a robot hand, and when the
wafer W is placed on the pusher pin 19•3 by the operation of the
robot hand, the pusher pin 19•3 slowly descends and places the
wafer W onto the electrostatic chuck. When the wafer is taken from the
electrostatic chuck, the opposite operation is made to pass the wafer W
to the robot hand. The surface material of the pusher pin 19•3
should be selected so as to eliminate the possibility that the wafer
position is shifted, and that the wafer is contaminated, silicon rubber,
fluorine rubber, ceramics such as SiC or alumina, a resin such as Teflon
or polyamide, or the like is desirably used.

[0339]There are several methods for the drive mechanism of the pusher pin
19•3. One is a method of placing a nonmagnetic actuator in the
lower part of the electrostatic chuck. This may include a method of
directly linear-driving the pusher pin by an ultrasonic linear motor, and
a method of linear-driving the pusher pin by a combination of a
rotational ultrasonic motor and a ball screw or rack & pinion gear. In
this method, the pusher mechanism can be compactly arranged on a table of
an XY stage on which the electrostatic chuck is mounted, the number of
wirings of the actuator, limit sensor and the like considerably
increases. The wiring extends from the table making XY motions to a
sample chamber (main chamber or main housing), but is bent with the
motion of the stage, and therefore it should be placed with a large
flexure R, and thus takes up a large space. Furthermore, the wiring may
become a particle source, and should be replaced periodically, and
therefore a necessary minimum number of wirings should be used.

[0340]Thus, as a different method, an external drive force is supplied.
When the stage moves to a position at which the wafer W is
attached/detached, a shaft protruding into a vacuum atmosphere through a
bellow is driven by an air cylinder provided outside a chamber to press a
shaft of a pusher drive mechanism provided in the lower part of the
electrostatic chuck. The shaft is connected to a rack pinion or link
mechanism in the pusher drive mechanism, and the reciprocating motion of
the shaft is associated with the vertical motion of the pusher pin. When
the wafer W is given and taken with the robot hand, the shaft is pushed
into the vacuum atmosphere with the air cylinder with the speed adjusted
at an appropriate level by a controller, whereby the pusher pin
19•3 is caused to rise.

[0341]Furthermore, the external source for driving the shaft is not
limited to the air cylinder, but may be a combination of the servo motor
and the rack pinion or ball screw. Furthermore, a rotating shaft can be
used as the external drive source. In this case, the rotating shaft
operates via a vacuum seal mechanism such as a magnetic fluid seal, and
the pusher drive mechanism includes a mechanism converting rotation into
a linear motion.

[0342]The correction ring 19•5 has an action of keeping uniform an
electric field distribution at end portion of the wafer, and a potential
essentially the same as that of the wafer is applied to the correction
ring 19•5. However, to eliminate influences of a very small gap
between the wafer and the correction ring and a very small difference in
surface height between the wafer and the correction ring, a potential
slightly different from that of the end portion of the wafer may be
applied. The correction ring has a width of about 10 to 30 mm in the
radial direction of the wafer, and a nonmagnetic and conductive material,
for example titanium, phosphor bronze, aluminum coated with TiN or TiC
may be used for the correction ring.

[0343]The conduction needles 19•4 is supported on a spring
19•7, and is lightly pressed against the back face of the wafer
with a spring force when the wafer is placed on the electrostatic chuck.
In this state, electric conduction with the wafer W is established by
applying a voltage as described above.

[0344]An electrostatic chuck main body is comprised of nonmagnetic plane
electrodes 19•1 and 19•2 made of tungsten or the like, and a
dielectric body formed thereon. For the material of the dielectric body,
alumina, aluminum nitride, polyimide or the like may be used. Generally,
ceramics such as alumina is a complete isolator having a specific volume
resistance of about 1014 Ωcm, and therefore causes no charge
transfer within the material, and a coulonbic force acts as absorption
force. On the other hand, by slightly adjusting a ceramic composition,
the specific volume resistance can be reduced to about 1010
Ωcm, whereby charge transfer occurs within the material, and thus
so called a Johnson-Rahbek force acts stronger than the coulonbic force
acts as a wafer absorption force. As the absorption force increases, the
applied voltage can be reduced accordingly, a larger margin for
insulation destruction can be provided, and a stable absorption force can
easily be obtained. Furthermore, by processing the surface of the
electrostatic chuck into, for example, a dimple shape, particles may fall
to a valley area of the dimple even if particles and the like are
deposited on the surface of electrostatic chuck surface, thus making it
possible to expect an effect of reducing the possibility that the
flatness of the wafer is affected.

[0345]From the above, a practical electrostatic chuck is such that
aluminum nitride or alumina ceramics adjusted to have a specific volume
resistance of about 1010 Ωcm is used as a material,
irregularities of dimple shape or the like are formed on the surface, and
the flatness of the surface formed by a set of the convexes is about 5
μm.

2-1-7-2) Chucking Mechanism for 200/300 Bridge Tool

[0346]The apparatus is required to inspect two types of 200 mm wafer and
300 mm wafer without mechanical modification. In this case, the
electrostatic chuck should chuck two types of wafer having different
sizes, and a correction ring matching the size of the wafer should be
placed on the periphery of the wafer. FIGS. 19(A), 19(B) and 20 show a
structure therefor.

[0347]FIG. 19 shows the wafer W of 300 mm placed on the electrostatic
chuck. The correction ring 19•1 having an inner diameter (gap of
about 0.5 mm) slightly larger than the size of the wafer W is positioned
in such a manner as to be interlocked with a metallic ring part on the
outer edge of the electrostatic chuck. The correction ring 19•1 are
provided with wafer dropping mechanisms 19•2 at three locations.
The wafer dropping mechanism 19•2 is driven by a vertical drive
mechanism associated with the drive mechanism of the pusher pin
19•3, and is supported rotatably about a rotating shaft provided in
the correction ring 19•1.

[0348]When the wafer W is received from the robot hand, the pusher pin
drive mechanism operates to push the pusher pin 19•3 upward. In
appropriate timing therewith, the wafer dropping mechanism 19•2
provided in the correction ring 19•1 rotates under a drive force as
shown in FIG. 19(B). Then, the wafer dropping mechanism 19•2 forms
a taper plane guiding the wafer W to the center of the electrostatic
chuck. Then, the wafer W is placed on the pusher pin 19•3 pushed
upward, and thereafter the pusher pin 19•3 was made to descend. By
appropriately adjusting action timing of the drive force for the wafer
dropping mechanism 19•2 together with the descending of the pusher
pin 19•3, the wafer W has its position corrected by the taper plane
of the dropping mechanism 19•2 and placed on the electrostatic
chuck so that the center of the wafer W almost matches the center of the
electrostatic chuck.

[0349]It is desired that a low frictional material such as Teflon,
preferably a conductive low frictional material (e.g. conductive Teflon,
conductive diamond like carbon, TIB coating) is formed on the taper plane
of the dropping mechanism 19•2. Furthermore, symbols A, B, C, D and
E in the figure denote terminals (described later) for applying a
voltage, and reference numeral 19•4 denotes a wafer conducting
needle for detecting that the wafer W is placed on the electrostatic
chuck, which is pushed upward by a spring 19•5.

[0350]FIG. 20 shows the wafer W of 200 mm placed on the same electrostatic
chuck. The surface of the electrostatic chuck is exposed because the
diameter of the wafer is smaller than that of the electrostatic chuck,
and therefore a correction ring 20•1 having a size so large that
the electrostatic chuck is completely covered. The positioning of the
correction ring 20•1 is performed in the same manner as in the case
of the correction ring for the 300 mm wafer.

[0351]A step is provided on the inner edge of the correction ring
20•1, and the correction ring 20•1 is fitted in a ring groove
20•2 on the electrostatic chuck side. This is a structure for
covering the surface of the electrostatic chuck with a conductor
(correction ring 20•1) so that the surface of the electrostatic
chuck is not seen through a gap between the inner edge of the correction
ring 20•1 and the outer edge of the wafer W when the 200 mm wafer
is placed. This is because if the surface of the electrostatic chuck is
exposed, the surface of the electrostatic chuck is electrically charged
to disturb the potential of the sample surface when an electron beam is
applied.

[0352]Replacement of the correction ring 20•1 is performed by
providing a correction ring replacement space at a predetermined position
in a vacuum chamber, and conveying therefrom a correction ring having a
necessary size by a robot and attaching the correction ring to the
electrostatic chuck (inserting the correction ring into an interlocked
part).

[0353]The correction ring for the 200 mm wafer is provided with the wafer
dropping mechanism 20•2 as in the case of the correction ring for
the 300 mm wafer. A recess is formed on the electrostatic chuck side so
as not to interfere with the wafer dropping mechanism 20•2. The
method of placing the wafer on the electrostatic chuck is identical to
that for the 300 mm wafer. Furthermore, symbols A, B, C, D and E denote
terminals for applying a voltage, reference numeral 20•3 denotes a
push pin similar to the push pin 19•3, and reference numeral
20•4 denotes a wafer conducting needle similar to the wafer
conducting needle 19•4.

[0354]FIGS. 20-1(A) and 20-1(B) schematically show the configuration of
the electrostatic chuck capable of coping with both types of 300 mm wafer
and 200 mm, in which FIG. 20-1(A) shows the 300 mm wafer placed on the
electrostatic chuck, and FIG. 20-1(B) shows the 200 mm wafer placed on
the electrostatic chuck. As apparent from FIG. 20-1(A), the electrostatic
chuck has a width large enough to place the 300 mm wafer thereon, and as
shown in FIG. 21-2(B), the central area of the electrostatic chuck has a
width large enough to place the 200 mm wafer thereon, and a groove
20•6 in which the inner ridge of the correction ring 20•1 is
to be fitted is provided in such a manner as to surround the wafer.
Furthermore, symbols A, B, C, D and E denote terminals for applying a
voltage.

[0355]In the case of the electrostatic chuck shown in FIGS. 20-1(A) and
20-1(B), whether the wafer is placed on the electrostatic chuck, whether
the wafer is correctly placed on the electrostatic chuck, whether the
correction ring exists, and so on are optically detected. For example, by
placing an optical sensor above the electrostatic chuck, and detecting an
optical path length when light emitted from the optical sensor is
reflected by the wafer and returned back to the optical sensor, whether
the wafer is placed horizontally or slantingly can be detected.
Furthermore, existence/nonexistence of the correction ring can be
detected by providing a light transmitter slantingly irradiating an
appropriate point in a space where the correction ring should be placed,
and a light receiver receiving reflected light from the correction ring.
Further, by providing a combination of the light transmitter slantingly
irradiating the appropriate point in the space where the correction ring
for the 200 mm wafer should be placed and the light receiver receiving
reflected light from the correction ring, and a combination of the light
transmitter slantingly irradiating the appropriate point in the space
where the correction ring for the 300 mm wafer should be placed and the
light receiver receiving reflected light from the correction ring, and
detecting which light receiver receives reflected light, which of the
correction ring for the 200 mm wafer and the correction ring for the 300
mm wafer is placed on the electrostatic chuck can be detected.

2-1-7-3) Wafer Chucking Procedure

[0356]The wafer chucking mechanism having the structure described above
chucks the wafer according to the following procedure.

[0357](1) A correction ring matching the size of the wafer is carried by a
robot and placed on the electrostatic chuck.

[0358](2) The wafer is placed on the electrostatic chuck by transportation
of the wafer by a robot hand and vertical motions of the pusher pin.

[0359](3) A voltage is applied to the electrostatic chuck in a dipole type
(positive and negative voltages are applied to terminals C and D) to
adsorb the wafer.

[0360](4) A predetermined voltage is applied to a conducting needle to
destruct an insulation film (oxide film) on the back face of the wafer.

[0361](5) A current between terminals A and B is measured to check whether
conduction with the wafer is established.

[0362](6) A transition of the electrostatic chuck to a unipole type
adsorption is made (terminals A and B are set to GRD, and the same
voltage is applied to terminals C and D).

[0363](7) The voltage of the terminal A (, B) is decreased while keeping a
difference in potential between the terminal A (, B) and the terminal C
(,D), and a predetermined retarding voltage is applied to the wafer.

2-1-8) Apparatus Configuration for 200/300 Bridge Tool

[0364]The configuration for achieving an apparatus capable of inspecting
the 200 mm wafer and the 300 mm wafer without mechanical modification is
shown in FIG. 21 and FIG. 22. Aspects in which the apparatus is different
from the apparatus dedicated for the 200 mm wafer or the apparatus
dedicated for the 300 mm wafer will be described below.

[0365]At an installation site 21•1 of the wafer cassette that is
replaced for specifications of the 200/300 mm wafer, FOUP, SMIF, the open
cassette and the like, the wafer cassette appropriate to the wafer size
and the type of wafer cassette determined depending on user
specifications can be placed. An atmosphere transportation robot
21•2 has a hand capable of coping with different wafer sizes, i.e.
a plurality of wafer dropping portions are provided in conformity with
the wafer sizes, and the wafer is placed on the hand at a location
matching the wafer size. The atmosphere transportation robot 21•2
sends the wafer from the installation site 21•1 to a pre-aligner
21•3, regulates the orientation of the wafer, then takes the wafer
from the pre-aligner 21•3, and sends the wafer into a load lock
chamber 21•4.

[0366]A wafer rack in the load lock chamber 21•4 has a similar
structure, a plurality of dropping portions matching wafer sizes are
formed in a wafer support portion of the wafer rack, the height of the
robot hand is adjusted so that the wafer placed on the hand of the
atmosphere transportation robot 21•2 is placed in the dropping
portion matching the size of the wafer, the wafer is inserted into the
wafer rack, and then the robot hand descends to place the wafer in a
predetermined dropping portion of the wafer support portion.

[0367]The wafer placed on the wafer rack in the load lock chamber
21•4 is then taken from a load lock chamber 21•3 by a vacuum
transportation robot 21•6 installed in a transfer chamber
21•5, and conveyed onto a stage 21•8 in the sample chamber
21•7. The hand of the vacuum transportation robot 21•6 has a
plurality of dropping portions matching wafer sizes as in the case of the
atmosphere transportation robot 21•2. The wafer placed in a
predetermined dropping portion of the robot hand is placed on the
electrostatic chuck having previously mounted a correction ring
21•9 matching the wafer size in the stage 21•8, and fixedly
adsorbed by the electrostatic chuck. The correction ring 21•9 is
placed on a correction ring rack 21•10 provided in the
transportation chamber 21•5. Then, the vacuum transportation robot
21•6 takes the correction ring 21•9 matching the wafer size
from the correction ring rack 21•10, and conveys the correction
ring 21•9 onto the electrostatic chuck, fits the correction ring
21•9 in a positioning interlocked part formed on the outer edge of
the electrostatic chuck, and then places the wafer on the electrostatic
chuck.

[0368]When the correction ring is replaced, the opposite operation is
carried out. That is, the correction ring 21•9 is removed from the
electrostatic chuck by the robot 21•6, the correction ring is
returned back to the correction ring rack 21•10 in the transfer
chamber 21•5, and the correction ring matching the size of the
wafer to be inspected next is conveyed from the correction ring rack
21•10 to the electrostatic chuck.

[0369]In the inspection apparatus shown in FIG. 21, the pre-aligner
21•3 is located close to the load lock chamber 22•4, and
therefore the wafer is easily returned back to the pre-aligner for
realignment if alignment of the wafer is not adequate enough to place the
correction ring in the load lock chamber, thus bringing about an
advantage that time loss in the step can be reduced.

[0370]FIG. 22 shows an example of changing a site where the correction
ring is placed, in which the correction ring rack 21•10 is omitted.
In the load lock chamber 22•1, the wafer rack and the correction
ring rack are formed in a layered form, and they can be placed in an
elevator to move vertically. First, to place the correction ring matching
the size of the wafer to be inspected next on the electrostatic chuck,
the vacuum transportation robot 21•6 moves the elevator of the load
lock chamber 22•1 to a position where the correction ring can be
taken out. When, the correction ring is placed on the electrostatic chuck
by the vacuum transportation robot 21•6, then the elevator is
manipulated so that the wafer to be inspected can be transferred, and the
wafer is taken from the wafer rack by the vacuum transportation robot
21•6, and then placed on the electrostatic chuck. This
configuration requires an elevator in the load lock chamber 22•1,
but can downsize the vacuum transportation chamber 21•5, and is
thus effective in reducing a foot print of the apparatus.

[0371]Furthermore, a sensor detecting whether or not the wafer exists on
the electrostatic chuck is desirably placed at a position such that the
sensor can cope with any of different wafer sizes, but if it is
impossible, a plurality of sensors working in the same manner may be
placed for each wafer size.

[0372]The inspection apparatus described with respect to FIG. 21 employs a
procedure in which the correction ring is placed on the electrostatic
chuck, and the wafer is positioned so that the wafer fits the inner
diameter of the correction ring. Then, the inspection apparatus shown in
FIG. 22 employs a procedure in which the correction ring is mounted on
the wafer in the load lock chamber 22•1, and the wafer with the
correction ring mounted thereon is conveyed together with the correction
ring into the sample chamber 21•7, and mounted on the electrostatic
chuck on the stage. Mechanisms for realizing the procedure include an
elevator mechanism for vertically moving an elevator to pass the wafer
from the atmosphere transportation robot to the vacuum transportation
robot, shown in FIGS. 22-1 and 22-2. A procedure of conveying the wafer
using this mechanism will be described below.

[0373]As shown in FIG. 22-1 (A), the elevator mechanism provided in the
load lock chamber has multistage (two-stage in the figure) correction
ring supports base so situated as to be movable in the vertical
direction. An upper-stage correction ring support base 22•2 and
lower-stage correction ring support base 22•3 are fixed on a first
base 22•5 rising/descending with rotation of a first motor
22•4, whereby the first base 22•5 and upper and lower
correction ring support bases 22•2 and 22•3 move upward or
downward with rotation of the first motor 22•4.

[0374]The correction ring 22•6 having an inner diameter matching the
size of the wafer is placed on each correction ring support base. For the
correction ring 22•6, two types having different inner diameters,
i.e. the type for the 200 mm wafer and the type for the 300 mm wafer, are
prepared, and they have the same outer diameter. In this way, by using
correction rings having the same outer diameter, mutual compatibility is
provided, thus making it possible to place the correction ring in the
load lock chamber in an arbitrary combination of the correction ring for
the 200 mm wafer and the correction ring for the 300 mm wafer. That is,
for a line in which 200 mm wafers and 300 mm wafers flow in a mixed form,
inspection can be performed flexibly for either type of wafer with the
upper stage set for the 300 mm wafer and the lower stage set for the 200
mm wafer. Furthermore, for a line in which wafers of the same size flow,
wafers in upper and lower stages can be inspected alternately with upper
and lower stages set for the 200 mm or 300 mm wafer, thus making it
possible to improve the throughput.

[0375]A second motor 22•7 is placed on the first base 22•5,
and a second base 22•8 is vertically movably attached to the second
motor 22•7. An upper wafer support base 22•9 and a lower
wafer support base 22•10 are fixed on the second base 22•8.
Consequently, when the second motor 22•7 rotates, the second base
22•8 and upper and lower wafer support bases 22•9 and
22•move upward or downward in one united body.

[0376]Then, as shown in FIG. 22-1(A), the wafer W is placed on the hand of
the atmosphere transportation robot 21•2 and loaded into the load
lock chamber 22•1, and then as shown in FIG. 22-1(B), the second
motor 22•7 is rotated in a first direction to move the wafer
support bases 22•9 and 22•10 upward to place the wafer W on
the upper-stage wafer support base 22•9. In this way, the wafer W
is moved from the atmosphere transportation robot 21•1 to the wafer
support base 22•9. Thereafter, as shown in FIG. 22-1(C), the
atmosphere transportation robot 21•2 is moved backward, and when
the backward movement of the atmosphere transportation robot 21•2
is completed, the second motor 22•7 is rotated in a direction
opposite to the first direction to move the wafer support bases
22•9 and 22•10 downward as shown in FIG. 22-1(D). In this
way, the wafer W is placed on the correction ring 22•6 in the
upper-stage.

[0377]Then, as shown in FIG. 22-1(E), the hand of the vacuum
transportation robot 21•6 is introduced into the load lock chamber
22•1 and stopped at below the correction ring 22•6. In this
state, the first motor 22•4 is rotated, and as shown in FIG.
22-1(F), the first base 22•5, the upper and lower correction ring
support bases 22•2, 22•3, the second motor 22•7, and
the upper and lower wafer support bases 22•9 and 22•10 are
moved downward, whereby the correction ring 21•6 placed on the
upper-stage wafer support base 22•9, and the wafer W can be placed
on the hand of the vacuum transportation robot 21•6 and loaded into
the sample chamber 21•7.

[0378]The operation of returning the wafer inspected in the sample chamber
21•7 back to the load lock chamber 21•4 is carried out in a
procedure opposite to the procedure described above, and the wafer loaded
onto the wafer support base together with the correction ring by the
vacuum transportation robot is transferred to the correction ring support
base, then to the wafer support base, and finally placed on the
atmosphere transportation robot. Furthermore, in FIGS. 22-1 and 22-2, the
operation of giving and taking the wafer in the upper stage is described,
but the same operation can be carried out in the lower stage by adjusting
the heights of the hands of the atmosphere transportation robot
21•2 and the vacuum transportation robot 21•6. In this way,
by appropriately changing the heights of the hands of the atmosphere
transportation robot 21•2 and the vacuum transportation robot
21•6, the wafer that has not been inspected yet can be loaded into
the sample chamber from one stage, and then the inspected wafer can be
unloaded to the other stage from the sample chamber in an alternate
manner.

2-2) Method for Transportation of Wafer

[0379]Transportation of the wafer from the cassette 13•12 supported
by the cassette holder 13•2 to the stage apparatus 13•6
placed in the working chamber 13•16 will now be described in order
(see FIGS. 14 to 16).

[0380]If the cassette is manually set as described previously, the
cassette holder 13•2 having a structure suitable for this
application is used, while if the cassette is automatically set, the
cassette holder 13•2 having a structure suitable for this
application is used. In this embodiment, when the cassette 13•12 is
set on the lift table 13•13 of the cassette holder 13•2, the
lift table 13•13 is made to descend by the lift mechanism
13•14, and the cassette 13•12 is matched with the entrance
13•15. When the cassette is matched with the entrance 13•15,
a cover (not shown) provided in the cassette is opened, a cylindrical
cover is placed between the cassette and the entrance 13•15 of the
mini-environment apparatus 13•3 to isolate the inside of the
cassette and the inside of the mini-environment space from the outside.
The structures thereof are well known, and therefore detailed
descriptions of the structures and functions are not presented.
Furthermore, if a shutter apparatus for opening and closing the entrance
13•15 is provided on the mini-environment apparatus 13•3
side, the shutter apparatus operates to open the entrance 13•15.

[0381]On the other hand, the arm 16•16 of the first transportation
unit 16•14 is stopped while being oriented in any of the direction
M1 and the direction M2 (oriented in the direction M1 in this
description), and when the entrance 13•15 is opened, the arm
extends to receive one of wafers housed in the housing at the leading
end. Furthermore, adjustment of the position of the arm and the wafer to
be taken from the cassette in the vertical direction is performed with
the vertical movement of the drive unit 16•15 of the first
transportation unit 16•14 and the arm 16•16 in this
embodiment, but it may be performed with the vertical movement of the
lift table of the cassette holder or with both the vertical movements.

[0382]When the reception of the wafer by the arm 16•16 is completed,
the arm contracts and operates the shutter apparatus to close the
entrance (if the shutter apparatus exists), and then the arm 16•16
rotates about the axial line O1-O1 so that it can extend in the
direction M3. Then, the arm extends to place the wafer placed on the
leading end or held by the chuck on the pre-aligner 16•5, and the
orientation of the wafer in the rotational direction (orientation about
the central axial line perpendicular to the wafer plane) is positioned
within a predetermined range by the pre-aligner 16•5. When the
positioning is completed, the transportation unit 16•14 receives
the wafer from the pre-aligner 16•5 at the leading end of the arm,
and then makes the arm contract so that the arm can be extend in the
direction M4. Then, the door 13•27 of the shutter apparatus
14•8 moves to open entrances 13•25 and 13•37, and the
arm 16•16 extends to place the wafer on the upper stage or lower
stage side of the wafer rack 14•11 in the first loading chamber
14•2. Furthermore, before the shutter apparatus 14•8 is
opened to pass the wafer to the wafer rack 14•11 as describe
previously, the opening 17•4 formed in the partition wall
14•5 is air-tightly closed with the door 14•19 of the shutter
apparatus 14•10.

[0383]In the process of transportation of the wafer by the first
transportation unit 16•14, clean air flows (as a down flow) in
laminar form from the gas supply unit 16•9 provided on the housing
of the mini-environment apparatus 13•3 to prevent deposition of
dust on the wafer during transportation. Part of air around the
transportation unit (about 20% of air supplied from the supply unit,
which is mainly contaminated air, in this embodiment) is suctioned from
the suction duct 16•12 of the discharge apparatus 16•4 and
discharged to the outside of the housing. Remaining air is collected via
the collection duct 16•10 provided on the bottom of the housing and
returned back to the gas supply unit 16•9.

[0384]When the wafer is placed in the wafer rack 14•11 in the first
loading chamber 14•2 of the loader housing 13•5 by the first
transportation unit 16•14, the shutter apparatus 14•8 is
closed to seal the loading chamber 14•2. Then, an inert gas is
filled in the first loading chamber 14•2 to purge air, and then the
inert gas is discharged to create a vacuum atmosphere in the loading
chamber 14•2. The vacuum atmosphere of the first loading chamber
14•2 may have a low degree of vacuum. When a satisfactory degree of
vacuum is achieved in the loading chamber 14•2, the shutter
apparatus 14•10 operates to open the shutter 14•5 of the
entrance 17•4 closed with the door 14•19, the arm 14•20
of the second transportation unit 14•12 extends to receive one
wafer from the wafer seat 14•11 by a holding apparatus at the
leading end (placing the wafer on the leading end, or holding the wafer
by a chuck mounted at the leading end). When the reception of the wafer
is completed, the arm contracts, and the shutter apparatus 14•10
operates again to close the entrance 17•4 with the door
14•19.

[0385]Furthermore, before the shutter apparatus 14•10 is opened, the
arm 14•20 takes a posture in which the arm 14•20 can extend
in the direction N1 of the wafer rack 14•11. Furthermore, entrances
14•7 and 14•1 are closed with the door 14•9 of the
shutter apparatus 13•29 before the shutter apparatus 14•10 is
opened as described previously, communication between the second loading
chamber 14•3 and the working chamber 13•16 is inhibited in an
air-tight state, and the second loading chamber 14•3 is evacuated.

[0386]When the shutter apparatus 14•10 closes the entrance
17•4, the second loading chamber 14•3 is evacuated again to
have a degree of vacuum higher than that of the first loading chamber
14•2. In the meantime, the arm of the second transportation unit
16•14 is rotated to a position in which it can extend toward the
stage apparatus 13•6 in the working chamber 13•16. On the
other hand, in the stage apparatus 13•6 in the working chamber
13•16, the Y table 13•33 moves upward to a position in which
the center line X0-X0 of the X table 13•34 almost matches
the X axis line X1-X1 passing through the rotation axis line
O2-O2 of the second transportation unit 14•12 in FIG. 14,
and the X table 13•34 moves to a position close to the leftmost
position in FIG. 14, and waits in this state. When the degree of vacuum
of the second loading chamber 14•3 is approximately the same as
that of the working chamber 13•16, the door 14•9 of the
shutter apparatus 13•29 moves to open the entrances 14•7 and
14•1, and the arm extends so that the leading end of the arm
holding the wafer approaches the stage apparatus 13•6 in the
working chamber 13•16. The wafer is placed on the holding surface
14•14 of the stage apparatus 13•6. The placement of the wafer
is completed, the arm contracts, and the shutter apparatus 13•29
closes the entrances 14•7 and 14•1.

[0387]Since the stage has a mechanism applying a backward bias potential
(retarding potential) to the wafer, the arm is made to have a potential
identical or close to that of the stage, or the arm is made to have a
floating potential when the arm goes to place or take the wafer, whereby
a trouble such as a discharge due to a short of the potential is avoided.
Furthermore, as another embodiment, the bias potential to the wafer may
be kept off when the wafer is conveyed onto the stage apparatus.

[0388]If the bias potential is controlled, the potential is kept off until
the wafer is conveyed to the stage, and the bias potential may be turned
on and applied after the wafer is conveyed to the stage. For timing of
applying the bias potential, tact time is preset, and the bias potential
may be applied based on the tact time, or placement of the wafer on the
stage is detected with a sensor, and the bias potential may be applied
using the detection signal as a trigger. Furthermore, the closing of the
entrances 14•7 and 14•1 by the shutter apparatus 13•29
is detected, and the bias potential may be applied using the detection
signal as a trigger. Further, if the electrostatic chuck is used,
adsorption by the electrostatic chuck is confirmed, and this may be used
as trigger to apply the bias potential.

[0389]The operation of conveying the wafer in the cassette 13•12
onto the stage apparatus has been described above, and for returning the
wafer, which has been placed on the stage apparatus 13•6 and
processed, from the stage apparatus 13•6 into the cassette
13•12, the operation opposite to that described above is made.
Furthermore, since a plurality of wafers are placed on the wafer rack
14•11, the wafer can be conveyed between the cassette and the wafer
rack 14•11 in the first transportation unit 16•14 while the
wafer is conveyed between the wafer rack 14•11 and the stage
apparatus 13•16 in the second transportation unit 14•12, thus
making it possible to carry out inspection processing efficiently.

[0390]Specifically, if a processed wafer A and an unprocessed wafer B
exist in the wafer rack 14•11, the unprocessed wafer B is first
moved to the stage 13•6. In the mean time, the processed wafer A is
moved from the wafer rack to the cassette 13•12 by the arm, and an
unprocessed wafer C is taken from the cassette 13•12 by the arm,
positioned by the pre-aligner 16•5, and then moved to the wafer
rack 14•11 of the loading chamber 14•2.

[0391]In this way, in the wafer rack 14•11, the processed wafer A
can be replaced with the unprocessed wafer C while the wafer B is
processed. Furthermore, depending on the use of the apparatus for
performing inspection and evaluation, a plurality of stage apparatuses
13•6 are placed side by side, and the wafer is moved to each
apparatus from one wafer rack 14•11, whereby a plurality of wafers
can be subjected to the same processing.

[0392]FIG. 23 shows an alteration example of a method of supporting the
main housing 13•4. In the alteration example shown in FIG. 23, a
housing supporting apparatus 23•1 is composed of a thick and
rectangular steel plate 23•2, and the housing main body 23•3
is placed on the steel plate. Thus, a bottom wall 23•4 of the
housing main body 23•1 is thinner than the bottom wall of the
embodiment described previously. In an alteration example shown in FIG.
24, a housing main body 24•3 and a loader housing 24•4 are
supported in a suspended state by a frame structure 24•2 of a
housing supporting apparatus 24•1.

[0393]The lower ends of a plurality of longitudinal frames 24•5
fixed to the frame structure 24•2 are fixed at four corners of a
bottom wall 24•6 of the housing main body 24•3, and a
circumference wall and a top wall are supported by the bottom wall. An
anti-vibration apparatus 24•7 is placed between the frame structure
24•2 and a base frame 24•8. Furthermore, the loader housing
24•4 is suspended by a suspending member 24•9 fixed to the
frame structure 24•2. In the alteration example of the housing main
body 24•3 shown in this figure, the total weight at the center of
gravity of the main housing and various kinds of devices provided therein
can be reduced owing to the support in a suspended manner. In the method
for supporting the main housing and the loader housing including the
above alteration example, vibrations from the floor are not transferred
to the main housing and the loader housing.

[0394]In another alteration example (not shown), only the housing main
body of the main housing is supported from below by the housing
supporting apparatus, and the loader housing can be placed on the floor
in the same manner as the case of the adjacent mini-environment apparatus
13•3. Furthermore, in still another alteration example, only the
housing main body of the main housing 13•4 is supported by the
frame structure in a suspended manner, and the loader housing can be
placed on the floor in the same manner as the case of the adjacent
mini-environment apparatus.

[0395]According to the embodiments described above, the following effects
can be exhibited.

(1) The entire configuration of a projection electron microscope type
inspection apparatus using an electron beam can be obtained, and an
inspection object can be processed with high throughput.(2) Clean air is
flowed through the inspection object in the mini-environment space to
prevent deposition of dust, and a sensor for observing the cleanness is
provided, whereby the inspection object can be inspected while monitoring
dust in the space.(3) Since the loading chamber and the working chamber
are integrally supported via the vibration preventing apparatus, the
inspection object can be supplied to the stage apparatus and inspected
without being influenced by the external environment.

2-3) Electro-Optical System

2-3-1) Overview

[0396]The electro-optical system 13•8 comprises an electro-optical
system comprising a primary electro-optical system (hereinafter referred
to simply as primary optical system) 25.notlessthan.schematically shown
in FIG. 25-1, provided in a column 13•38 fixed to the housing main
body 13•17, and a secondary electro-optical system (hereinafter
referred to simply as secondary optical system) 25•2, and a
detection system 25•3. The primary optical system 25•1 is an
optical system irradiating an electron beam to the surface of the wafer W
as an inspection object, and comprises an electron gun 25•4
emitting an electron beam, a lens system 25•5 comprised of an
electrostatic lens converging a primary electron beam emitted from the
electron gun 25•4, a Wien filter or E×B separator 25•6,
and an objective (or cathode) lens system 25•7, and they are placed
in order with the electron gun 25•4 situated at the uppermost
position as shown in FIG. 25-1. A lens constituting the objective lens
system 25•7 of this embodiment is a retarding electric field
objective lens. In this embodiment, the optical axis of the primary
electron beam emitted from the electron gun 25•4 is slanted with
respect to the axis (perpendicular to the surface of the wafer) of
irradiation beam irradiated to the wafer W as an inspection object. An
electrode 25•8 is placed between the objective lens system
25•7 and the wafer W as an inspection object. The electrode
25•8 is axially symmetric with respect to the axis of irradiation
beam of the primary electron beam, and voltage-controlled by a power
supply 25•9.

[0397]The secondary optical system 25•2 comprises a lens system
25•10 comprised of an electrostatic lens penetrable to secondary
electrons separated from the primary optical system by the E×B type
deflector 25•6. This lens system 25•10 functions as a
magnifying lens magnifying a secondary electron image.

[0398]The detection system 25•3 comprises a detector 25•11 and
an image processing unit 25•12 placed on an imaging surface of the
lens system 25•10.

[0399]The direction of incident of the primary beam is usually the E
direction of the E×B filter (direction opposite to the electric
field), and this direction is identical to the integration direction of
an integration-type line sensor (TDI: time delay integration). The
integration direction of the TDI may be different from the direction of
the first beam.

[0400]The electron beam optical system column comprises the following
components.

(1) Column Magnetic Shield

[0401]A nickel alloy such as permalloy or a magnetic material such as iron
is suitably used for a member constituting the column, whereby an effect
of inhibiting the influence of magnetic disturbance can be expected.

(2) Detector Rotation Mechanism

[0402]To match the scan axis direction of the stage with the scan
direction of the detector, the column 13•38 has in its upper part a
detector rotation mechanism eliminating a deviation in the scan direction
caused by assembly of apparatus by allowing the detector 25•11 such
as the TDI to rotate at several degrees about the optical axis while
keeping the inside of the column 13•38 under vacuum. In this
mechanism, about 5 to 40 seconds are required for rotational resolution
and rotational position reproducibility. This arises from the requirement
that a deviation between the scan direction of the stage and the scan
direction of the detector should be about 1/10 of one pixel during the
scanning of an image of one frame. According to the detector rotation
mechanism, an angular error between the direction of movement of the
stage and the integration direction of the TDI can be adjusted to be 10
mrad or less, preferably 1 mrad or less, more preferably 0.2 mrad or
less.

[0403]One example of the configuration of the detector rotation mechanism
will be described below using FIGS. 25-3 to 25-5. FIG. 25-3 shows the
overall configuration of the detector rotation mechanism provided in the
upper part of the column 13•38, FIG. 25-4 is a schematic diagram of
a mechanism for rotating an upper column, and FIG. 25-5 shows a mechanism
for sealing the upper column and a lower column.

[0404]In FIG. 25-3, the upper end of the column 13•38 is comprised
of an upper column 25•20 having the detector 25•11 attached
thereto, and a lower column 25•21 fixed to the main housing
13•4. The upper column 25•20 is supported on the lower column
25•21 via a bearing 25•22 and can rotate about the optical
axis of the secondary optical system, and a seal portion 25•23 is
provided between the upper column 25•20 and the lower column
25•21 to keep the inside of the column 13•38 under vacuum.
Specifically, the seal portion 25•23 is placed between the lower
end of the upper column 25•20 and the upper end of the lower column
25•21, a flange portion 25•24 is provided at the upper end of
the lower column 25•21 in such a manner as to surround the upper
column 25•20, and the bearing 25•22 is placed between the
flange portion 25•24 and the side face of the upper column
25•20.

[0405]Bearing clamps 25•25 and 25•26 for clamping the bearing
25•22 are screwed to the upper column 25•20 and the lower
column 25•21, respectively. Further, to rotate the upper column
25•20 with respect to the lower column 25•21, a drive
mechanism shown in FIG. 25-4 is provided. That is, a raised portion
25•27 is provided in part of the bearing clamp 25•26 provided
at the upper end of the flange portion 25•24, while an actuator
25•29 is fixed on a mounting member (bracket) 25•28
protruding from the upper column 25•20. A shaft 25•30 of the
actuator 25•29 contacts the raised portion 25•27, and a
precompression spring 25•31 given a force for attraction toward the
raised portion 25•27 is provided between the flange portion
25•24 and the mounting member (bracket) 25•28 having the
actuator 29•29 fixed thereon. Consequently, by activating the
actuator 25•29 to change the length of the shaft 25•30
protruding from the actuator 25•29, the upper column 25•20
can be rotated at a desired angle in a desired direction with respect to
the lower column 25•21.

[0406]For the rotation accuracy described above, the movement resolution
of the actuator 25•29 is desirably 5 to 10 μm. Furthermore, the
actuator 25•29 may be a piezo actuator or actuator motor-driving a
micrometer. Furthermore, a sensor capable of measuring a relative
distance between the bracket 25•28 for fixing the actuator
25•29 and the raised portion 25•27 is desirably mounted to
measure a rotational position of the detector 25•11. For the
sensor, a linear scale, potentiometer, laser displacement meter,
deformation gage or the like may be used.

[0407]The seal portion 25•23 is placed so that a very small gap
25•32 (FIG. 25-5) is formed between the upper end face of the lower
column 25•21 and the lower end face of the upper column 25•20
as shown in FIG. 25-5 to keep the inside of the column 13•38 under
vacuum. The seal portion 25•23 comprises a partition ring
25•33 solidly fixed at the center, and two elastic seals
25•34 and 25•35, and springs 25•36 and 25•37 for
ensuring the contact pressure of the seal surface to improve a sealing
performance are provided between lip portions of the elastic seals
25•34 and 25•35, respectively. An air exhaust port
25•39 communicating with an air exhaust channel 25•38 formed
in the lower column 25•21 is provided at the center of the
partition ring 25•33. The elastic seals 25•34 and 25•35
are preferably made of a material having a very small frictional
coefficient and being excellent in slidability and for example, Omni-seal
manufactured by Huron Co., Ltd. (USA) may be used.

[0408]In this way, the elastic seal is doubly placed, and a space
25•40 between the elastic seals is evacuated, whereby even if the
upper column 25•20 rotates to cause a very small leak to occur in
the elastic seal 25•35 on the atmosphere side, the leaked air is
exhausted through the air exhaust channel 25•38, and thus the
pressure of the space 25•40 does not significantly increase.
Therefore, no leak occurs from the elastic seal 25•34 into the
column, so that the vacuum in the column is never degraded. The space
25•40 may be continuously evacuated, but it is also possible to
evacuate the space 25•40 only when the detector rotation mechanism
is activated. This is because the leak is more likely to occur when the
detector is rotated, and sufficient sealing is ensured with the pressure
of contact between the elastic seals 25•34 and 25•35 and the
lower end of the upper column 25•20 when the detector is not
rotated.

[0409]It is important that the pressure of contact between the elastic
seals 25•34 and 25•35 and the upper and lower surfaces is
appropriately set, and this can be realized by adjusting the size of the
gap 25•32. The adjustment of the gap 25•32 can be performed
by inserting a shim 25•41 between the bearing 25•22 and the
upper end face of the lower column 25•21. By inserting the shim
25•41 in this position, the height of the bearing 25•22 with
respect to the lower column 25•21 can be changed. On the other
hand, for the upper column 25•20, the bearing 25•22 is held
between clamps 25•25 and 25•26, and therefore the bearing
25•22 moves vertically together with the upper column 25•20,
and the gap 25•32 between the upper column 25•20 and the
lower column 25•21 changes by the thickness of the shim
25•41.

[0410]Furthermore, depending on specifications of the column, a sufficient
performance is obtained even if only a single seal is provided instead of
providing double seals and the space between seals is not evacuated as
shown in FIG. 25-5. However, double seals are more reliable, and allow a
high vacuum to be easily produced. Furthermore, the springs 25•36
and 25•37 are provided in the elastic seals 25•34 and
25•35 in the above description, but if the elastic seals
25•34 and 25•25 are sufficiently pressed against the upper
and lower surfaces with a pressure difference between the vacuum and the
atmosphere, or the elastic seals 25•34 and 25•35 themselves
have sufficient repulsive forces, the springs 25•36 and 25•37
may be omitted.

[0411]To match the direction of the detector with the direction of the
stage with the rotation mechanism having the configuration described
above, the detector 25•11 is rotated in a very small amount, the
scan imaging of the detector 25•11 is carried out on each such an
occasion, and the angle of the detector 25•11 is matched with the
angle when the most sharp image is obtained. A specific process thereof
will be described below.

[0412]In the rotatable range of the detector rotation mechanism, the
detector 25•11 is rotated at a very small angle to carry out the
scan imaging of the detector 25•11, and the obtained image is
subjected to image processing, whereby a numerical value allowing
evaluation of image quality such as a contrast is determined. This
process is repeated to determine a relation between the rotational
position of the detector 25•11 and the image quality, and a
rotational position for best image quality is determined. Then, the
detector 25•11 is rotated to the position to complete the operation
of positioning the detector 25•11.

[0413]An allowable value for a positional deviation between the stage and
the detector 25•11 depends on the requirement that a deviation
between the scan direction of the stage and the scan direction of the
detector should be about 1/10 of one pixel during the scanning of an
image of one frame in the detector 25•11. Thus, an allowable
angular deviation when pixels are arranged in 500 stages along the scan
direction is about 40 seconds.

[0414]To set the angular deviation between the stage and the detector to
40 seconds or less, a method in which the relation between the position
of the detector and the image quality described above is expressed as a
numerical value by a method such as multinomial approximation, and a
position of the detector 25•11 for best image quality is
determined, or a method in which the detector 25•11 is first
roughly rotated to form an image, an approximate relation between the
position of the detector and the image quality is determined, a range of
a position of the detector for best image quality is identified, the
detector is again rotated in a very small amount in this range to carry
out the same operation, and a position of the detector for best image
quality is accurately determined can be used. To prevent occurrence of an
angular deviation after matching the angles of the stage and the detector
in this way, it is effective to provide a lock mechanism. For example, a
planar part is placed between the bearing clamps 25•25 and
25•26, and this platy part and the bearing claims 25•25 and
25•26 are fixed together with a bolt.

(3) NA Movement Mechanism

[0415]The NA is held by a mechanism capable of moving several centimeters
along the optical axis or in a direction orthogonal to the light axis,
and allows an adjustment to be made so that the NA is situated at an
optically optimum position according to a change in magnifying power. A
plurality of NAs can be desirably mounted on a NA holding unit, and by
adding such a mechanism, the NA can be replaced while keeping the inside
of the column under vacuum when the NA is degraded or a change in
transmittance is desired.

[0416]Furthermore, a heater unit is desirably installed in the NA holding
unit to provide an effect of inhibiting degradation of the NA by keeping
the NA at a high temperature. Furthermore, it is effective to install a
piping unit for a reactive gas, so that the NA can be cleaned while
keeping the inside of the column under vacuum.

(4) Isolation Valve

[0417]A valve allowing the inside of the column to be partitioned into a
plurality of spaces is desirably installed in the column. Specifically,
it is effective to install the valve so that the space of an MCP unit or
electron gun unit can be separated from the space of the stage unit. Such
a configuration enables maintenance of the periphery of the stage and the
like to be carried out while keeping the MCP unit and the electron gun
unit under vacuum. Furthermore, conversely, maintenance of the MCP unit
and the electron gun unit can be carried out while keeping the stage unit
and the like under vacuum.

(5) Shield Barrel

[0418]The optical axis is preferably surrounded by a grounded cylindrical
member, and by providing such a configuration, an effect of inhibiting
the influence of electric external disturbance can be expected.

(6) Orifice Before MCP

[0419]An orifice-like or slim cylindrical member is placed between a
series of electro-optical system and the MCP unit reduces, and by
providing a configuration such that a conductance of a path extending
through a space between the electro-optical system and MCP unit, the
pressure of the MCP unit can be easily kept at about 1/5, preferably
about 1/10, more preferably about 1/100 of the pressure of the
electro-optical system.

(7) Integration of Electrodes and Enhancement of Accuracy

[0420]Parts required to be installed on an electro-optically concentric
axis with accuracy of several μm or smaller are desirably assembled by
a method such as inter-member combination processing or cooling fit.

(8) Optical Microscope

[0421]An optical microscope is provided to compare a sample image under
low magnifying power and an image seen under light with an electron beam
image. The magnification is about 1/10 to 1/5000, preferably about 1/20
to 1/1000, more preferably about 1/20 to 1/100 of that of electron beam
image. An image of light from the sample surface can be detected by a
two-dimensional solid imaging device (CCD), and displayed on a CRT.
Furthermore, it can be stored in a memory.

(9) Coaxial Ion Pump

[0422]By installing a non-vibration type vacuum pumping system such as an
ion pump rotation-symmetrically around an optical axis near the electron
gun unit and the MCP unit, an effect of keeping such a place under high
vacuum while offsetting the influences of charged particles and magnetic
fields by the pumping system itself can be expected. This is because a
reduction in conductance of piping is alleviated when the ion pump is
connected to the electron gun unit and the like to evacuate the same.

[0423]Specific embodiments will be described below.

(1) Embodiment 1

[0424]The embodiment is one example of inspection apparatus mainly
comprised of a vacuum chamber, a vacuum pumping system, a primary optical
system, a secondary optical system, a detector, an image processing unit
and a computer for control. One example thereof is shown in FIG. 26.

[0425]A primary optical system 26•1 for illuminating an electron
beam to a sample, and a secondary optical system 26•2 for guiding
electrons emitted from the sample surface, for example secondary
electrons, reflection electrons, back-scattered electrons, to the
detector are provided. The secondary optical system is a projection
electron microscope type optical system. A beam separator 26•3 of
E×B is used for separating the primary system and the secondary
system. Furthermore, an image signal of an electron detected by a
detector 26•4 is an optical signal or/and an electric signal, and
processed by an image processing unit 26•5. Furthermore, at this
time, if the number of electrons entering the detector is 200 or less per
one pixel equivalent area, an image can be formed satisfactorily. Of
course, the image can be satisfactorily formed if the number of electrons
is 200 or greater per one pixel area.

[0426]An electron gun 26•6 as a component of the primary optical
system uses LaB6 as a heat filament (cathode), and derives electrons
from a cathode with a Wenelt and draw electrode 26•7. Then, a beam
is converged to an aperture 26•9 with a two-stage A lens (Einzell
lens) 26•8 to form a crossover. Then, the beam passes through a
two-stage aligner 26•10, an aperture 26•11, a three-stage
quadrupole lens 26•12 and a three-stage aligner 26•13, enters
a beam separator, is deflected in the direction of the sample surface,
passes through an aperture 26•14 and a P lens (objective lens)
16•16 of the secondary system, and is applied to the sample surface
almost vertically.

[0427]The aligner (deflector) 26•10 making the beam to pass through
a beam area highly uniform in crossover and having a high luminance by
the aperture 26•9, and specifying an angle of a beam incident to
the quadrupole lens by the aperture 26•11 is used for adjustment to
cause the beam enter at the center of the optical axes of the aperture
26•11 and the quadrupole lens 26•12. The quadrupole lens
26•12 is used for deformation of the beam shape by changing paths
of the beam in two directions, for example X and Y directions. For
example, in the shape of the sample irradiation beam, a change in ratio
of shapes of circular, elliptic, rectangular and rectangular/elliptic
shapes in x and y directions can be achieved (see FIG. 27). After passing
through the quadrupole lens, the beam is adjusted to pass through an
aperture 26•15 and the center of the P lens (objective lens)
26•16 by the aligner 26•14, and enters the sample surface. At
this time, the shape of the irradiation beam can be symmetrically formed
for at least one of two axes. The beam may have an asymmetric shape.
Energy of the beam applied to the sample surface is finally determined by
a difference in voltage between the cathode and the sample surface. For
example, when the voltage of the cathode is 5.0 kV and the voltage of the
sample surface is 4 kV, energy of the irradiation beam is 1 keV (see FIG.
26).

[0428]In this case, the voltage error is ±10 V, and the energy error is
±20 eV. Furthermore, if secondary electrons are used as detection
electrons, the sample is negatively charged, and secondary electrons are
emitted from the sample in this state, made to form an image under
magnification by the secondary optical system, and guided to the
detection system when the beam irradiation energy of 1.5 keV±10 eV to
5 keV±10 eV is used. If the irradiation energy is 50±10 eV to 1500
eV±10 eV, the sample surface is positively charged, and emitted
secondary electrons are guided to the detection system. When the sample
is positively charged, the operation can be carried out with a relatively
low damage, but the sample is more easily influenced by charge-up or
unevenness in surface potential due to the charge-up. In the negative
charge operation, an image can be easily obtained with stability, and the
influence of charge-up or distortion of the image due to unevenness in
surface potential by the charge-up can be reduced compared to the case of
positive charge.

[0429]Furthermore, at the location of the aperture 26•15, the
operation may be carried out with positions of crossovers of the
secondary system and the primary system deviated from each other. For
example, the crossover of secondary electrons is formed on the center of
the secondary system optical axis for the secondary system, and the
crossover of the primary system is formed at a position deviated by 50 to
500 μm from the center of the optical axis of the secondary system
(may be either X or Y). Consequently, two crossovers of the primary
system and the secondary system never overlap each other in the aperture
26•15, and the current density can be alleviated, thus making it
possible to inhibit expansion of blurs due to the space charge effect
when the amount of beam current is large. This is effective when the
current density of the primary system irradiation beam is greater than
1×10-3 A/cm2, for example. For any lower current density,
there is no influence even if the centers of optical axes are identical.

[0430]For electrons emitted from the sample surface, at least one type of
secondary electrons, reflection electrons and back scattered electrons
are used. The levels of energy emitted from the sample surface are 0 to
10 eV, 1000 eV±10 eV and 10 to 1000 eV, respectively, for incident
beam energy of 1000 eV±10 eV, for example. Furthermore, electrons
passing through a thin film or a bored sample (e.g. slancil mask) are
used. In this case, for the former thin sample, the incident energy is
reduced by the amount equivalent to the thickness of the sample, and for
the bored sample, the incident energy remains unchanged.

[0431]A focused ion beam (FIB) may be used instead of the electron beam. A
Ga ion source of a liquid metal is generally used as the FIB source, but
other liquid metal ion source using a metal that is easily liquefied, or
an ion source of a different type, for example a duoplasmatron using a
discharge may be used.

[0432]For the sample, various samples such as a tip of about 10×10
mm, and 2, 4, 6, 8 and 12 inch wafers are used. Particularly, it is
effective in detection of defects of a wiring pattern having a line width
of 100 nm or smaller and a via having a diameter of 100 nm or smaller,
and contaminants, and also convenient for detection of electric defects
of the pattern and the via. For the sample, Si wafers, semiconductor
device wafers made by processing Si, micromachined wafers, substrates for
liquid crystal displays, head-processed wafers for hard disks and the
like are used.

[0433]For the secondary system 26•2, an example will be described in
which a projection type optical system to make electrons emitted from the
sample, for example secondary electrons, reflection electrons,
back-scattered electrons and transmission electrons form an image under
magnification and guide the electrons to the detection system is used. As
an example of the lens configuration of a column, the lens is constituted
by a P lens (objective lens) 26•16, the aperture 26•15, the
aligner 26•14, the beam separator 26•3, a P lens
(intermediate lens) 26•17, the aligner 26•18, the aperture
26•19, a P lens (projection lens) 26•20, an aligner
26•21, and a micro-channel plate (MCP) unit. A hermetic quartz
glass is placed on an upper flange of the column. A relay lens and a
two-dimensional charge coupled device (2D-CCD) are placed thereon, and an
image formed on a fluorescent screen is formed on a 2D-CCD sensor.

[0434]Emitted electrons from the sample surface form a crossover in the
aperture 26•15 at the P lens (objective lens) 26•16, and are
made to form an image at the center of the beam separator 26•3. The
operation under conditions of forming an image at the center of the beam
separator is effective because the effect of an aberration of a secondary
beam occurring in the beam separator 26•3 can be reduced to a low
level. This is because for example, the deflection amount/aberration
varies depending on the image height when the beam is made to pass at
E×B, and therefore the aberration suffered by image formation
components can be reduced to a minimum due to formation of the image.
Since this is also true for the primary system, not only image formation
conditions are formed on the sample but also an image formation point is
formed near the center of the beam separator, whereby the aberration of
the primary beam is reduced, and unevenness of the current density on the
sample is effectively reduced.

[0435]To adjust the beam to be situated at the center of the P lens
(intermediate lens) 26•17 thereon, the aligner 26•14 is used.
To adjust the beam to be situated at the center of the P lens (projection
lens) 26•20 in the upstream thereof, the aligner 26•18 is
used. To adjust the beam to be situated at the center of the MCP thereon,
the aligner 26•21 exists. The magnification of the P lens
(objective lens) 26•16 is 1.5× to 3×, the magnification
of the P lens (intermediate lens) 26•17 is 1.5× to 3×,
and the magnification of the P lens (projection lens) 26•20 is
30× to 50×. To achieve these magnifications, a voltage
appropriate to each of the magnifications is applied to each lens to make
an adjustment. Furthermore, to make a fine adjustment of a focus, a
dedicated focus correction lens is incorporated in the P lens (objective
lens) system, and focusing is achieved by fine adjustment of the voltage
applied to the electrode. At locations of the aperture 26•15 and
the aperture 26•19, the aperture 26•15 can be used to cut
noises, and the aperture 26•19 can be used so that it plays a role
to determine an aberration/contrast if the crossover is formed in both
cases.

[0436]For the size, for example, the aperture 26•15 and the aperture
26•19 can be used at φ30 to φ2000 μm, preferably φ30
to φ1000 μm, more preferably φ30 to φ500 μm. At this
time, if the aberration, the transmittance and the contrast
characteristic are mainly determined with the aperture 26•15, the
aperture 26•15 is used at, for example, φ30 to φ500 μm,
and the aperture 26•19 is used at φ1000 to φ2000 μm. If
the aberration, the transmittance and the contrast characteristic are
mainly determined with the aperture 26•19, for example, the
aperture 26•19 is used at φ30 to φ500 μm, and the
aperture 26•15 is used at φ1000 to φ2000 μm.

[0437]Furthermore, astigmatic electrodes may be placed above and below the
P lens (intermediate lens) 27•17. The electrodes are used to
correct an astigmatic aberration occurring due to the beam separator
26•3 and the like. For example, an astigmatic electrode having an
electrode configuration of 4, 6 or 8 poles can be used. For example,
different voltages may be applied to the eight electrodes to correct the
astigmatic aberration and the spherical aberration.

[0438]Furthermore, in the lens operation when a reflection electrode image
and back-scattered electrons are used, the P lens (projection lens)
26•20 in the last stage is effective in cutting noises of secondary
electrons if a retarding lens (negative voltage application lens) is used
for the P lens. Usually, the amount of secondary electrons is greater
than the amount of reflection electrodes by a factor of 10 to 1000, and
therefore the retarding lens is especially effective when image formation
is performed using reflection electrons/back-scattered electrons. For
example, when a cathode voltage of a primary system electron source is 4
kV, a sample potential is 3 kV, the level of reflection electron energy
from the sample is 1 keV, and when a detector voltage is an installation
voltage, a difference in energy level between the reflection electron and
the secondary electron is about 1 keV at the site of a P electrode. At
this time, in the negative voltage lens operation of the P lens
(projection lens), conditions such that the central voltage allows the
reflection electron to pass and cuts off the secondary electron can be
used. The conditions can be determined by means of simulation.

[0439]For the beam separator 26•3, a separator operating with
E×B where the electrode is orthogonal to the magnetic pole, or only
with a magnetic field B is used. As an example, an E×B is comprised
of an E electrode forming an electric field distribution and a magnetic
pole having a pole face orthogonal to the E electrode and forming a
magnetic flux density distribution in a direction orthogonal to the E
electrode. For example, when the optical axis of the secondary system is
perpendicular to the sample surface, the incident beam of the primary
system can be set at 10 to 90 degrees with respect to the axis of the
secondary system. At this time, the beam of the primary system is
deflected with E×B and can perpendicularly enter the sample
surface, and emitted electrons from the sample surface are guided in the
direction of the optical axis, i.e. in the direction perpendicular to the
sample surface with E×B. This is achieved by a voltage applied to
the E electrode, and a magnetic flux density formed in the B electrode.
For example, a voltage of ±2 kV±1 V is applied to a pair of E
electrodes, a magnetic flux density distribution is formed in parallel
from a pair of B electrodes and for example, at the center of E×B,
a magnetic flux density of 1 to 60 G±1 G in the direction of the
magnetic pole is produced (see FIG. 26).

[0440]Furthermore, E×B can also be applied to the inversed
deflection relation of the primary system and the secondary system. That
is, the incident beam source of the primary system is provided just above
the sample, the detector of the secondary system is provided at an angle
of 10 to 80 degrees with respect to the axis of the primary system, the
beam of the primary system is made to enter the sample without applying a
deflection force thereto with E×B, and the deflection force is
applied to electrons emitted from the sample (beam of secondary system),
whereby the electrons can be guided to the detector.

[0441]In the detector 26•4, signal electrons are introduced into an
electron multiplier tube 28•1 such as an MCP, and amplified
electrons are applied to a fluorescent screen to form a fluorescent
image. The fluorescent screen has a glass plate 28•2 such as quartz
glass coated with a fluorescent material on one side. The fluorescent
image is formed by a relay lens system 28•3 on a two-dimensional
CCD 28•4. This relay lens system and the CCD are placed on the
column. A hermetic glass 28•6 is placed on an upper flange of the
column, the vacuum environment in the column is separated from the
external atmospheric environment, the fluorescent image is formed on the
CCD with deformation/contrast degradation being reduced, and the
fluorescent image can be efficiently formed.

[0442]An integration-type line image sensor (TDI-CCD) camera can be used
instead of the CCD. In this case, TDI imaging can be performed while the
sample is stage-moved, for example, in the direction of the E electrode
or the direction of the B magnetic pole on the stage. For example, when
the number of TDI integration stages is 256, one stage has 2048 pixels,
the element size is 15×15 μm, and the magnification of the MCP
image formation with respect to the sample surface is 300×, the
size of the sample surface may be 30/30 μm for the MCP surface if the
line/space is 0.1/0.1 μm. When the magnification of the relay lens is
1×, imaging is performed with the size of two elements being
equivalent to 30 μm. At this time, electrons emitted from the sample
position equivalent to one element, i.e. the sample size of
0.05×0.05 μm are integrated during movement on the stage
equivalent to 256 element stages, and the total amount of acquired light
increases to allow imaging to be performed. This is especially effective
when the stage speed is high such as a speed corresponding to a line rate
of 100 kHz to 600 kHz. This is because when the line rate is high, the
number of acquired electrons per element, i.e. the intensity of acquired
light per element of the TDI sensor decreases, and thus integration can
be carried out to enhance the final density of acquired light and
increase the contrast and S/N. The line rate is 0.5 kHz to 100 MHz,
preferably 1 kHz to 50 MHz, more preferably 20 kHz to 10 MHz. In
correspondence therewith, a video rate is 1 to 120 MHz/tap, preferably 10
to 50 MHz/tap, more preferably 10 to 40 MHz/tap. Furthermore, the number
of taps is 1 to 520, preferably 4 to 256, more preferably 32 to 128 (see
FIGS. 28 and 29).

[0443]The CCD and the TDI sensor/camera that are used have characteristics
of low noises and high sensitivities. For example, they can be set at 100
to 100000 DN/(nJ/cm2) but above all, if they are used at 1000 to
50000 DN/(nJ/cm2), the efficiency is improved. Further, if they are
used at 10000 to 50000 DN/(nJ/cm2), a high quality image can be
obtained with good S/N even when the line rate is high.

[0444]Furthermore, when the image is acquired using the CCD or TDI sensor,
it can be used in a state in which a region of the number of
pixels×the number of stages almost matches an area irradiated with
the primary beam, thus improving efficiency and reducing noises. For the
noise, electrons from a site of a large image height other than areas
miscellaneously used may reach the detector as noises. To reduce these
noises, it is effective to reduce beam irradiations at a site other than
an effective field. Image information acquired by the CCD or TDI sensor
is converted into an electric signal, and subjected to data processing by
an image processor. Through this image processing, image comparison is
carried out on a cell-to-cell, die-to-die, die-to-any die basis, and thus
defects can be inspected. For example, pattern defects, particle defects,
and potential contrast defects (e.g. electric connection defects of
wiring and plating) are inspected.

[0445]For the stage 26•22, a stage installed with a combination of
at least one of X, Y, Z and θ movement mechanisms is used. In this
electron beam inspection apparatus, the following components can be used
as the components described above.

[0451]The detector can be used in the combinations described above. The
MCP has a function to amplitude entering electrons, and the electrons
exiting therefrom are converted into light by the fluorescent screen. If
the amount of entering electrons is so large that they are not required
to be amplified, the operation can be performed without the MCP.
Furthermore, a scintillator can be used instead of the fluorescent
screen. A light signal thereof (or image signal) is transmitted to the
TDI or forms an image under a predetermined magnification in the case of
the relay lens, and under a magnification of 1× (light signal is
transmitted in a ratio of 1:1) in the case of the FOP. The
photomultiplier amplifies a light signal and converts the light signal
into an electric signal, and the multi-photomultiplier has a plurality of
photomultipliers arranged.

[0453]In the electron beam inspection apparatus, an irradiation beam shape
of the primary beam symmetrical with respect to at least one axis of X
and Y axes can be used. Accordingly, an acquired image can formed with a
low aberration and low deformation on the electron beam entrance surface
of the detector by the beam having an optical axis at the center.

[0454]Furthermore, if the CCD or TDI is used as the detector, a sufficient
S/N ratio can be achieved in an area corresponding to one pixel, for
example in an area where the number of entering electrons is 200/pixel or
smaller in formation of one pixel on the MCP, thus making it possible to
use the detector for image processing and defect detection. In the
projection type optical system, for example, noise cut and aberration
reduction effects can be achieved by specifying the size of the aperture
26•15 or 26•19, and therefore by placing an aperture having a
diameter of 30 μm to 1000 μm, for example, an improvement in S/N
ratio can be achieved, thus making it possible to acquire an image of
high resolution and high quality in an area of 200 electrons/pixel.

[0455]TDI performs integration equivalent to the number of stages for the
direction of movement of the stage. Integration equivalent to 256 stages
is performed in this embodiment, but the number of integration stages is
appropriately 114 to 8192, preferably 114 to 4096, more preferably 512 to
4096. Even if there is slight unevenness in illuminance of the primary
beam in the direction of integration, and there is unevenness in signal
electrons from the sample, the unevenness is equalized due to the effect
of integration, and detected electron information is constant and stable.
Thus, in consideration of a direction where unevenness in illuminance of
the primary electron beam easily occurs, the direction of movement of the
stage can be determined so that the direction where the illuminance
unevenness easily occurs matches the direction of integration of the TDI.
The image can be continuously acquired by using the TDI, but the CCD may
be used to scan the stage in the step and repeat mode to acquire the
image. That is, the operation of stopping the stage at a specific
location to acquire an image, then moving the stage to a next location,
and stopping the stage there to acquire an image is repeated. A similar
operation can be carried out using the TDI. That is, the still mode of
the TDI (pause image acquirement mode, in which the stage is stopped) is
used, or an image of a certain area (e.g. 2048 pixels×2048 pixels)
is acquired by a usual image acquirement process of the TDI, and then the
stage is moved to a next location (no image is acquired during the
movement), where an image is similarly acquired. Thus, in this case,
inspection is performed without stopping the movement of the stage.

[0456]When the appearance of the sample surface is magnified by electrons
to form an image on the detector, an aberration, a blur and the like of
the secondary optical system is desirably within one pixel if the
resolution of the image is limited to about one pixel of the CCD or TDI.
Since the aberration and the blur grow if electrons are deflected at
E×B, signal electrons such as secondary electrons, reflection
electrons and back-scattered electrons are adjusted to travel in straight
lines with no deflection force given thereto in the secondary optical
system in this embodiment. That is, the central axis of the secondary
optical system is a straight line passing through the center of the field
of view of the sample, the center of E×B and the center of the
detector.

[0457]Furthermore, since cases other than the embodiment described above
are acceptable as long as no blur occurs in the image of the secondary
optical system, such cases are included in this invention as a matter of
course.

(2) Embodiment 2

[0458]When the TDI sensor/camera is used for the detector in the
inspection apparatus similar to the embodiment 1, the image can be
acquired more quickly and efficiently if the number of images/stages is
2048 to 4096, the number of taps is 32 to 128, and the sensitivity is
10000 to 40000 DN/(nJ/cm2). At this time, the line rate may be 100
to 400 kHz, and the video rate may be 10 MHz to 40 MHz. At this time, the
operation is capable of being done when an 8 inch Si wafer, for example
LSI device wafer is used, the resolution is 0.1 μm/pixel, and
inspection time per one wafer is 1/8 to 2 hours.

[0459]At this time, when the resolution is 0.1 μm/pixel, a contrast of
3 to 30% is achieved, and thus image observation and defect detection can
be sufficiently performed even with a pattern shape of, for example,
LS:0.2/0.2 μm in sample observation and defect inspection. A defect
having a shape other than L/S can be detected by comparison using a
change in contrast as long as the defect has a size of one pixel or
greater. A contrast of 5 to 30% is achieved, thus making it possible to
perform observation and defect inspection by image processing.
Furthermore, for the LSI device wafer, defects of the design rule or
smaller can be detected. Defects equivalent to the half pitch of the
wiring width can be detected for the memory, and defects equivalent to
the gate length can be detected for the logic.

[0460]When defects are detected using the TDI sensor/camera and an image
processing mechanism, the image can be continuously formed to perform
inspection continuously by the TDI operation. At this time, the sample is
placed on the stage, and continuous operations are similarly carried out
to obtain the image. The speed of the stage is essentially determined by
v=f×D, wherein v represents a stage speed, f represents a line
frequency and D represents a size corresponding to sensor pixels on the
sample (determined by a projection magnification). For example, when f is
300 kHz and D is 0.1 μm, v equals 30 mm/s.

[0461]FIG. 29 shows an example of a detection system having a
configuration different from that of the embodiment 1 shown in FIG. 28.
In this case, an MCP 29•2, an FOP 29•3, a TDI sensor/package
29•4, a contact pin 29•5 and a field-through flange
29•6 are provided in a column 29•1 under vacuum, and an
output of the TDI sensor 29•4 is received by a TDI camera
29•7 through the field-through flange 29•6. Furthermore, the
FOP 29.3 is coated with a fluorescent material to form a fluorescent
image by electrons from the MCP 29•2. The fluorescent image is
transmitted to the TDI sensor 29•4 by the FOP 29•3. An image
signal of the TDI sensor 29•4 is transmitted to the TDI camera
29•7 via the contact pin 29•5 and the field-through flange
29•6. At this time, use of the FOP 29.3 can reduce an optical
signal transmission loss. For example, the transmittance increases by a
factor of about 5 to 20 compared the relay lens. This is especially
effective when the TDI operation is carried out. This is because quicker
activation is possible due to high intensity of the acquired optical
signal, and signal unevenness of a fiber shape is reduced to a negligible
level by integration of the TDI. Here, the contact pin 29•5 for
connecting pins of the TDI sensor 29•4 and the field though flange
29•6 is required. The contact pin 29•5 is connection-fixed to
one side (e.g. pin of field-through) by fit contact, and contacts the pin
of the TDI sensor/package with an elastic force of a spring (not shown).

[0462]Consequently, the pin of the field-through flange 29•6 and the
pin of the TDI sensor/package 29•4 can be installed with a low
pressing force, in a parallel position and at a low impedance. In a high
speed operation sensor, a large number of pins are used and for example,
more than 100 pins are required. If the number of pins is large, the
installation pressure (pressing force) increases, and thus the TDI
sensor/package 29•4 may be broken. Such points have been overcome
to make installation possible.

[0463]As shown in FIG. 28, the CCD or TDI is usually installed at the
atmosphere side, and the MCP and the fluorescent screen are installed
under vacuum, but by placing the CCD or TDI under vacuum, the relay
optical system such as the FOP can be curtailed, thus making it possible
to improve transmission efficiency.

(3) Embodiment 3

[0464]In this embodiment, an EB-CCD or EB-TDI is used for the detector
(see FIG. 30) in the embodiments 1 and 2. The EB is an electron beam, and
the EB-CCD or EB-TDI directly inputs the electron beam, and converts it
into an electric signal (not detecting an optical signal).

[0465]Use of the EB-TDI sensor/camera can inject electrons directly into
an image portion of the sensor, accumulate charges. This means that it is
unnecessary to use the fluorescent screen, the relay lens and hermetic
glass used in the usual detector. That is, since an electric signal can
be obtained directly from an electron signal without temporarily
converting an electron signal image into an optical signal image, and
thus a loss associated with the conversion can be considerably reduced.
That is, image deformation by the fluorescent screen, hermetic glass and
the relay lens system, degradation in contrast, and deleterious effects
such as variations in magnification can be considerably reduced.
Furthermore, due to reduction in the number of components, downsizing,
cost-reduction and quick operations can be achieved. Quick operations can
reduce a signal transmission speed loss and an image formation speed
loss.

[0466]One example of a unit of the EB-TDI is shown in FIG. 30. See the
embodiment 1 for the optical system. The surface of a TDI sensor
30•3 is placed in the upper part of a secondary system column, i.e.
on the image-forming point the upper part of the P lens (projection
lens). The unit is comprised of a TDI sensor/package 30•3, a
contact pin 30•4, a field-through 30•5, a TDI camera
30•1, and image processor 30•6 and a control PC 30•7.
Emitted electrons (any of secondary electrons, reflection electrons and
back-scattered electrons) from the sample surface are made to form an
image by the secondary system and enter the surface of the TDI sensor
30•3. Charges are accumulated in accordance with the amount of
electrons, and an electric signal for image formation is formed by the
TDI camera 30•1.

[0467]A pin of the sensor package 30•3 and a pin of the
field-through flange 30•5 are connected together by the contact pin
30•4. In this aspect, this embodiment is similar to the embodiment
2. In this case, since an electric image signal is converted directly
into an electric signal by the TDI sensor 30•3, components and
parts can be curtailed and the transmission channel can be shortened
compared to the detectors of the embodiments 1 and 2. This makes it
possible to achieve improvement in S/N due to reduction in noises, speed
enhancement, downsizing and cost-reduction.

[0468]The EB-TDI 30•1 is used in this embodiment, but the EB-CCD may
be similarly used. Particularly, this configuration is effective if the
number of required pins is greater than 100 due to a large number of
pixels or to perform high speed operations. A contact pin for connecting
the pin of the field-through and the package is required. The contact pin
is constituted by a spring material and a contact plate on one side (e.g.
on the package side), and can reduce the contact width. If there are a
large number of contact pins, for example 100 or more contact pins, a
pressing force at the time of connection increases, and if the total
force exceeds 5 kg, a problem of rupture of the package arises. Thus, a
contact pin having a pressing force limited to 50 to 10 g/pin by
adjustment of a spring force is used.

[0469]Furthermore, the number of incident electrons is insufficient when
the EB-CCD or EB-TDI is used, an MCP being an electron multiplier tube
can be used. Furthermore, for the number of images/stages, the number of
stages, the number of taps, the line rate and the video rate, conditions
similar to those of the embodiments 1 and 2 may be used. The sensitivity
can be 0.1 to 10000 DN/electron.

(4) Embodiment 4

[0470]In the inspection apparatus similar to the embodiments 1, 2 and 3, a
primary system 31•1 has the same configuration, but a secondary
system 31•2 has a different configuration as shown in FIG. 31. To
achieve a higher resolution, a two-stage P lens (objective lens)
31•3, a two-stage P lens (intermediate lens) 31•5, and a
two-stage P lens (projection lens) 31•8 are used. Further, the P
lens (intermediate lens) is notably a zoom lens. Consequently, a
projection-type beam optical system having a higher resolution and a
larger visual field size compared to conventional systems can be
achieved, and an image of any magnification can be acquired in the zoom
range.

2-3-2) Details of Configuration

[0471]An electron gun, a primary optical system, a secondary optical
system, an E×B unit, a detector and a power supply of an
electro-optical system shown in FIGS. 25-1 to 31 will be described in
detail below.

2-3-2-1) Electron Gun (Electron Beam Source)

[0472]A thermal electron beam source is used as an electron beam source.
An electron emission (emitter) material is LaB6. Any other
material can be used as long as the material has a high melting point
(low vapor pressure at high temperature) and a small work function. A
material having the leading end formed into a conic shape, or a material
having a conic shape with the leading end cut off is used. The diameter
of the leading end of the truncated cone is about 100 μm. For other
types, an electric field emission type electron beam source or thermal
electric field emission type is used, but when a relatively wide area
(e.g. 100×25 to 400×100 μm2) is irradiated with a
large amount of current (about 1 μA) as in the present invention, a
thermal electron source using LaB6 is most suitable.
Furthermore, in the SEM system, a thermal electric field electron beam
source (TFE type) and a short key type are generally used. The thermal
electron beam source is a system in which the electron emission material
is heated to emit electrons, and the thermal electric field emission
electron beam source is a system in which a high electric field is
applied to the electron emission material to emit electrons, and an
electron beam emission portion is heated to stabilize the emission of
electrons. In this system, extraction of electron beams under efficient
conditions called shot key conditions can be performed by selecting the
temperature and the electric field intensity and recently, this system
has been often used.

2-3-2-2) Primary Optical System

[0473]A part forming an electron beam applied from an electron gun, and
irradiating an electron beam having a two-dimensional cross section such
as a rectangular, circular or elliptic cross section or a linear electron
beam onto the wafer surface is called a primary electro-optical system.
By controlling lens conditions of the primary electro-optical system, the
beam size and the current density are controlled. By an E×B filter
(Wien filter) at a primary/secondary electro-optical system connection
portion, a primary electron beam is made to enter the wafer at a right
angle (±5°, preferably ±3°, more preferably
±1°).

[0474]Thermal electrons emitted from a LaB6 cathode are made to
form an image on a gun diaphragm as a crossover image by a Wenelt, triple
anode lens, double anode, or single anode. An electron beam having the
angle of incidence to the lens modified by an illumination visual field
diaphragm is made to form an image on an NA diaphragm in a form of
rotational asymmetry by controlling a primary system electrostatic lens,
and then applied to the wafer surface. The rear stage of a quadrupole
lens of the primary system is comprised of a three-stage quadrupole (QL)
and a one-stage aperture aberration correcting electrode. The quadrupole
lens has a constraint of strict alignment accuracy, but notably has a
strong convergence action compared to the rotational symmetry lens, and
is capable of correcting an aperture aberration corresponding to a
spherical aberration of the rotational symmetry lens by applying an
appropriate voltage to the aperture aberration correcting electrode.
Consequently, a uniform plane beam can be applied to a predetermined
area. Furthermore, the electron beam can be scanned by a deflector.

[0475]The shape and area of the irradiation electron beam on the sample
surface includes the shape and area of an imaging area of the TDI-CCD on
the sample, and it is desirable that the illuminance in the electron beam
irradiation area is uniform, and illuminance unevenness is 10% or less,
preferably 5% or less, more preferably 3% or less.

[0476]The shape and area of the TDI-CCD in this embodiment is equivalent
to a pixel number of 2048×512, with the pixel size being 16
μm×16 μm, and therefore its overall shape is a rectangle of
about 32.8 mm×8.2 mm. When the magnification of the secondary
optical system is 160×, the irradiation area on the sample surface
is 1/160 of 32.8 mm×8.2 mm, and is therefore a rectangle of 205
μm×51.2 μm.

[0477]Thus, the electron beam irradiation area in this case is desirably a
rectangle including a rectangle of 205 μm×51.2 μm, but it may
be a rectangle having round corners, ellipse, circle or the like as shown
in FIG. 27-1 as long as its shape and area meets the above conditions.
When the magnification of the secondary optical system is 320×, the
irradiation area is 1/320 of 32.8 mm×8.2 mm, which is equivalent to
a rectangle of 102.4 μm×25.6 μm, thus being 1/4 of the
irradiation area with the magnification of 160×.

[0478]In this way, in the present invention, a beam with a relatively
large area including imaging areas of the TDI-CCD as a detector is
applied to the sample, the imaging areas on the sample correspond to
pixels of the TDI-CCD, respectively, and electrons emitted from these
imaging areas on the sample are made to form an image on the TDI-CCD at a
time to perform detection.

[0479]The irradiation shape of the electron beam may be linear, and may be
scanned to ensure an irradiation are the same as that of a plane beam. A
linear beam 27•1 refers to a beam having a shape in which the
length-to-width ratio is 10:1 or greater as shown in FIGS. 27-2(1-1) and
27(1-2), it is not limited to a rectangle but may be an ellipse.
Furthermore, the linear beam 27•1 may have interrupted at some
midpoint as shown in FIG. 27-2(2). The scanning of the beam reduces the
time period over which the beam is continuously applied to the same
location of the sample, and thus has an advantage that the influence of
charge up on the sample is reduced.

[0480]FIGS. 27-2(3) and 27-2(4) show a relation between a multi-pixel
imaging area 27•3 of the TDI-CCD and the linear beam 27•1 on
an inspection subject 27•2. Among them, in FIG. 27-2(3), the linear
beam 27•1 is placed at almost a right angle (e.g.
90°±3°, preferably 90°±1°) with respect
to an integration direction 27•4 of the TDI-CCD or a direction of
movement 27•5 of the XY stage, and a direction of scan 27•6
of the beam is identical to the integration direction 28•4 or the
direction of movement 27•5 of the XY stage (e.g.
0°±1°, preferably 0°±1 minute, more preferably
0°± 1 second).

[0481]FIG. 27-2(4) shows another example, in which the linear beam
27•1 is almost parallel to the integration direction 27•4 of
the TDI-CCD or the direction of movement of the XY stage (e.g.
90°±1°, preferably 90°±1 minute, more
preferably 90°±3 seconds).

2-3-2-3) Secondary optical system

[0482]A two-dimensional secondary electron image produced by an electron
beam applied to the wafer is formed at a visual field throttling position
by an electrostatic lens equivalent to an objective lens, and magnified
and projected by a lens (PL) in the rear stage. This image formation and
projection optical system is called a secondary electro-optical system. A
negative bias voltage (retarding electric field voltage) is applied to
the wafer. The retarding electric field has an effect of retarding the
irradiation beam to reduce damage on the sample, and accelerating
secondary electrons generated from the sample surface with a difference
in potential between the objective lens and the wafer to reduce a color
aberration. Electrons converged by the objective lens are made to form an
image on the FA by the intermediate lens, and the image is magnified and
projected by the projection lens, and formed on a secondary electron
detector (MCP). In this optical system, the NA is placed between the
objective lens and the intermediate lens, and optimized to constitute an
optical system capable of reducing an off-axis aberration.

[0483]To correct a production-related error of the electro-optical system,
and an astigmatic aberration and an anisotropic magnification of an image
occurring with passage through an E×B filter (Wien filter), an
electrostatic octupole (STIG) is placed to make a correction, and an
axial shift is corrected with a deflector (OP) placed between lenses. In
this way, a projection type optical system with a uniform resolution in
the visual field can be achieved.

[0484]The optical system will be further described using a few
embodiments.

(1) Embodiment 5

[0485]FIG. 32 shows an electro-optical system. Primary electrons emitted
from an electron gun 32•1 pass through an image formation lens
32•2, then a two-stage zoom lens 32•3 and then a three-stage
quadrupole 32•4, and are deflected at 35° by an E×B
filter 32•5, and applied to the sample surface through an objective
lens 32•7 in an opposite direction in parallel to the optical axis
of a secondary optical system 32•6. Furthermore, for the quadrupole
lens, a multipole lens having two or more poles may be used, and not only
a lens having an even number of poles but also a lens having an odd
number of poles may be used. Furthermore, the quadrupole lens has 3 to 20
stages, preferably 3 to 10 stages, more preferably 3 to 5 stages.

[0486]Secondary electrons, reflection electrons and back-scattered
electrons emitted from the sample surface with irradiation of primary
electron beam are made to form an image at the center of the E×B
filter 32•5 by the objective lens 32•7, subjected to scaling
by an intermediate lens 32•8, and then made to form an image just
before a projection lens 32•9. The image formed with the
intermediate lens 32•8 is magnified by a factor of about 30 to 50
by the projection lens 32•9 and formed on the detector surface
32•10.

[0487]The image formation lens 32•2 enables an image to be formed
just before the zoom lens 32•3 even if the accelerating voltage is
changed, and is constituted by a one-stage lens in FIG. 32, but may be
constituted by a multiple-stage lens.

[0488]If the accelerating voltage of primary electron beam is fixed, the
irradiation area and shape of primary electron beam on the sample surface
almost depends on the conditions of the zoom lens 32•3 and the
conditions of the quadrupole lens 32•4. The zoom lens 32•3
changes the irradiation area during maintaining the beam shape. The
quadrupole lens 32•4 can change the size of the beam, but is used
mainly to change the beam shape (length-to-width ratio of ellipse). FIG.
32 shows the two-stage zoom lens 32•3 and the three-stage
quadrupole lens 32•4, but the number of stages may be increased.

[0489]The case will be discussed below where the size of one pixel of the
detector is 16 μm×16 μm, and the size of the detector is
2048×512 pixels. When the magnification of the secondary optical
system 32•6 is 160×, the size on the sample equivalent to one
pixel is 16 μm/160=0.1 μm, and the observation area is
204.8×51.2 μm. The irradiation area covering the observation
area has an elliptic shape, and thus changes in a variety of ways
depending on the ratio between the long axis and the short axis of the
ellipse. This situation is shown in FIG. 33. In FIG. 33, the horizontal
axis shows the position of the long axis and the longitudinal axis shows
the position of the short axis. In consideration of the optimum
irradiation shape, it is not desired that the beam is applied to areas
other than an observation area 33•1. To achieve the optimum
irradiation shape, an irradiation shape with the largest irradiation
efficiency obtained by dividing the area of the observation area by the
area of the irradiation area should be found.

[0490]FIG. 34 shows a plot of the ratio of the long axis to the short axis
in the shape of the irradiation area versus the irradiation efficiency.
From this plot, it can be understood that a shape with the best
irradiation efficiency is provided when the ratio of the long axis to the
short axis in the irradiation elliptic shape equals the ratio of the long
axis to the short axis in the rectangular observation area. That is, a
beam shape for thoroughly irradiating the observation area of
204.8×51.2 μm is a beam shape of 290×72.5 μm. In fact,
the shape of the irradiation beam slightly grows due to influences of the
aberration of the irradiation optical system and illuminance unevenness
of the electron gun. To achieve this irradiation beam shape, the
quadrupole lens 32•4 may be adjusted so that an image just before
the quadrupole lens 32•4 forms an elliptic irradiation area on the
sample surface by an optical system including the quadrupole lens
32•4 and the objective lens 32•7. In this case, it is only
required that a necessary irradiation area and a sufficiently uniform
irradiation current density over the entire irradiation area should be
obtained, and it is not necessary to make the irradiation beam form an
image on the sample surface. The size of the image just before the
quadrupole lens 32•4 is adjusted with the zoom lens 32•3 so
that a predetermined irradiation area can be obtained on the sample
surface.

[0491]Now, for example, assume that the magnification of the secondary
electro-optical system 32•6 is changed from 160× to
320×. At this time, the size equivalent to one pixel on the sample
surface is 0.05 μm×0.05 μm (16 μm/320=0.05 μm), and the
observation area is 102.4×25.6 μm. If the irradiation area is
kept at a magnification of 160× in this state, the amount of a
signal reaching one pixel of the detector is proportional to the area
ratio, and therefore equals 1/4 of the signal amount when the
magnification is 160×. Provided that an image of a signal amount
corresponding to average 400 electrons per pixel is seen when the
magnification is 160×, the standard deviation of fluctuations by
shot noises at this time is (400)=20. Accordingly, the S/N ratio is
400/20=20. To obtain an image of the same S/N ratio when the
magnification is 320×, the same signal amount should be within one
pixel. The area per pixel on the sample is 1/4 of the original area, and
accordingly the secondary electron signal amount density per unit area
should be quadrupled.

[0492]If landing energy represented as a difference in acceleration energy
of primary electrons and the potential of the sample surface is fixed,
the irradiation current density is approximately proportional to the
secondary electron signal amount density. Thus, it can be understood that
the irradiation current density should be quadrupled. To quadruple the
irradiation current density, the irradiation current should be simply
quadrupled, or the irradiation area should be reduced to 1/4 of the
original area. To reduce the irradiation area to 1/4 of the original
area, the irradiation size should be reduced to 1/2 of the original size
for both the long and short axes. Since both the observation area and
irradiation area are analogously scaled down by a factor of 2, the
observation area can be sufficiently irradiated.

[0493]As means for increasing the irradiation current density, the
irradiation current may be increased, or the irradiation area may be
decreased. However, it is more desirable that the irradiation area is
reduced, taking it consideration that areas other than the observation
area are preferably prevented from being irradiated.

[0494]Table 3 shows the voltages of the primary optical system lens and
the obtained irradiation sizes on the sample for secondary optical system
magnifications of 320× and 160×, respectively. As a result,
an irradiation area capable of sufficiently keeping up with the secondary
optical system magnification can be obtained. Although not shown in Table
3, the irradiation size for the magnification of 80× may be an
ellipse of 620 μm×180 μm, and the irradiation size for the
magnification of 480× may be an ellipse of 100 μm×30
μm. In this way, it is desirable that the irradiation size is changed
according to a change or shift in magnification.

[0495]If the observation area is illuminated with an electron beam, a
method in which a plurality of electron beams each having an area smaller
than the observation area are scanned to illuminate the observation area
can be used other than the method in which the observation area is
illuminated with a rectangular or elliptic electron beam having an area
covering the entire observation area. The number of beams is 1 to 1000,
preferably 2 to 100, more preferably 4 to 40. A linear beam with two or
more beams linked together may be scanned. In this case, by scanning the
beam in a direction perpendicular to the long direction of the line, a
wider area can be inspected with one scan. In this case, the CCD or TDI
may be used for the detector. To form a linear beam, for example, an
electron source of LaB6 is used, and the beam is made to pass
through a linear slit in the optical system. Furthermore, a cathode with
an electron source having a sharp and slender leading end may be used to
form a linear beam. Furthermore, the stage is moved continuously or
intermittently in at least one of directions of the XY plane during scan
of the beam so that the entire inspection area is covered.

(2) Embodiment 6

[0496]FIG. 35 shows the configuration of a detection system using a relay
lens. Secondary electrons made to form an image on the surface of an MCP
(micro-channel plate) 35•1 in the secondary optical system are
amplified according to a voltage applied to between the electron
incidence surface and the emission surface of the MCP 35•1 while
passing through a channel in the MCP 35•1. The structure and
operation of the MCP 35•1 are well known, and thus are not
described in detail here. In this embodiment, the pixel size on the MCP
35•1 is 26 μm, and the diameter of the channel in an effective
area of 1024 pixels wide and 512 pixels long is 6 μm. Electrons
amplified in the MCP 35•1 are emitted from the emission surface of
the MCP 35•1, and enter a fluorescent screen 35•3 coated on
an opposite glass plate 35•2 having a thickness of about 4 mm to
generate fluorescence having an intensity consistent with the amount of
electron signal. Since a thin transparent electrode is coated between the
glass plate 35•2 and the fluorescent screen 35•3 and a
voltage of about 2 to 3 kV is applied to between the electrode and the
MCP emission surface, expansion of electrodes between the MCP and the
fluorescent screen is restricted as much as possible to avoid the blur of
the image. Further, since electrons emitted from the MCP 35•1 enter
the fluorescent screen 35•3 with appropriate energy, luminous
efficiency is improved. Furthermore, the materials of the transparent
electrode and the glass plate 35•2 coated with the fluorescent
screen 35•3 may be any materials as long as they allow light to
pass efficiently.

[0497]A light intensity signal, into which an electric signal is converted
on the fluorescent screen 35•3, passes through the glass plate
35•2, then through an optically transparent plate 35•4
insulating vacuum from the atmosphere, then through a relay lens
35•5 imaging light generated on the fluorescent screen 35•3,
and enters a light receiving surface 35•6 of a CCD or TDI sensor
placed at the imaging position. In this embodiment, the relay lens
35•5 has an imaging scale factor of 0.5, and a transmittance of 2%.

[0498]Light impinging on the light receiving surface 35•6 is
converted into an electric signal by the CCD or TDI sensor, and the
electric signal of the image is outputted to an uptake apparatus. The TDI
sensor used in this embodiment has a pixel size of 13 μm, 2048
horizontal effective pixels, 144 integration stages, and 8 taps and a
maximum line plate of 83 kHz, but a TDI sensor having a larger number of
horizontal effective pixels and integration stages may be used in view of
technological advance of the TDI sensor in the future. Furthermore, the
structure and operation of the TDI sensor are known, and thus are not
described in detail here.

[0499]In Table 4, the secondary electron emission current density, the
secondary optical system imaging scale factor, the number of pixel
incident electrons obtained when the TDI line rate is determined, the TDI
gray scale pixel tone value and the stage speed in this embodiment are
shown in the columns of the Embodiment 1.

The full scale of the gray scale pixel tone value described here is 255
DN. This is due to the fact that the current MCP dynamic range is no more
than 2 μA. An epoch-making improvement in MCP dynamic range cannot be
currently expected, and therefore to obtain a certain pixel tone value,
it is important that minimum 200 DN/(nJ cm2) of TDI responsivity is
ensured.

(3) Embodiment 7

[0500]FIG. 36 shows the configuration of a detection system using an FOP.
The structure and operation of a fluorescent screen 36•1 and the
like are the same as those of the embodiment 5. However, the effective
area of an MCP 36•2 in this embodiment has a pixel size of 16
μm, which is equivalent to 2048 (wide)×512 (long) pixels. Unlike
the embodiment 5, a fluorescent screen 36•1 is coated on an FOP
(fiber optic plate) 36•3 having a thickness of about 4 mm, instead
of the glass plate. A light intensity signal, into which an electric
signal is converted at the fluorescent screen 36•1, passes through
fibers of the FOP 36•3. The light emission surface of the FOP
36•3 is coated with a transparent electrode, and this provides a
ground potential. Light emitted from the FOP 36•3 passes through
another FOP 36•4 with the thickness of, for example, 3 mm
contacting the FOP 36•3 with no gap therebetween, and enters the
light receiving surface of a CCD or TDI sensor 36•5 placed on the
light emission surface of the FOP 36•4 via an optically transparent
adhesive. Since light is not scattered over fibers of the FOP, image
quality is not significantly influenced if the pixel size of the CCD or
TDI sensor 36•5 is sufficiently larger than the fiber diameter.

[0501]In this embodiment, the fiber diameter of the FOP is 6 μm, and
the pixel size of the TDI sensor 36•5 is 16 μm. By making the
incidence side and the emission side of the FOP have different fiber
diameters, the magnification of the image can be changed, but this causes
deformation and distortion to grow, and therefore the fiber diameters are
the same in this embodiment. The transmittance is about 40% in this
embodiment.

[0502]The CCD or TDI sensor 36•5 is placed under vacuum, and an
electric signal 36•6 of the image, into which an optical signal is
converted, is outputted to an uptake apparatus through a field through
36•7 insulating the atmosphere from vacuum.

[0503]The CCD or TDI sensor 36•5 may be placed under the atmosphere,
and the atmosphere may be insulated from vacuum by the FOP, but in
consideration of reduction in transmittance and growth of deformation
with an increase in thickness of the FOP, such a configuration is less
likely positively adopted.

[0504]The TDI sensor 36•5 used in this embodiment has a pixel size
of 16 μm, 2048 horizontal effective pixels, 512 integration stages,
and 32 taps and a maximum line plate of 300 kHz, but a TDI sensor having
a larger number of horizontal effective pixels and integration stages may
be used in view of technological advance of the TDI sensor in the future.

[0505]The secondary electron emission current density, the secondary
optical system imaging scale factor, the number of pixel incident
electrons obtained when the TDI line rate is determined, the TDI gray
scale pixel tone value and the sage speed in this embodiment are shown in
the columns of the embodiment 2 in Table 4.

(4) Embodiment 8

[0506]FIG. 37(A) schematically shows the configuration of a projection
electron microscope type defect inspection apparatus EBI, and FIG. 37(B)
schematically shows the configurations of a secondary optical system and
a detection system of the defect inspection apparatus EBI. In FIG. 37, an
electron gun 37•1 has a thermal electron emitting LaB6 cathode
37•2 capable of operating under a large current, and primary
electrons emitted in a first direction from the electron gun 37•1
pass through a primary optical system including a several-stage
quadrupole lens 37•3 to have the beam shape adjusted, and then pass
through a Wien filter 37•4. The traveling direction of primary
electrons is changed to a second direction by the Wien filter 37•4
so that they are inputted to a sample W as an inspection object. Primary
electrons leaving the Wien filter 37•4 and traveling in the second
direction have the beam diameter reduced by an NA aperture plate
37•5, pass through an objective lens 37•6, and is applied to
the sample W.

[0507]In this way, in the primary optical system, a high luminance
electron gun made of LaB6 is used as the electron gun 37•1,
and thus making it possible to obtain a primary beam having a large
current and a large area with low energy compared to the conventional
scanning defect inspection apparatus. The electron gun 37•1 is made
of LaB6, has a truncated conic shape and a diameter of 50 μm or
greater, and can extract electrons at an intensity of 1×103
A/cm2sr to 1×108 A/cm2sr at a primary electron draw
voltage of 4.5 kV. The intensity is preferably 1×105
A/cm2sr to 1×107 A/cm2sr at 4.5 kV. The intensity is
further preferably 1×106 A/cm2sr to 1×107
A/cm2sr at 10 kV. Furthermore, the electron gun 37•1 can also
extract electrons at an intensity of 1×106 A/cm2 sr to
2×1010 A/cm2 sr at a primary electron extraction voltage
of 4.5 kV as a shot key type. The intensity is preferably
1×106 A/cm2 sr to 5×109 A/cm2sr at 10 kV.
Furthermore, a shot key type made of ZrO may be used for the electron gun
37•1.

[0508]The shape of an irradiation area in which primary electrons are
applied to the sample W is approximately symmetric to two other
orthogonal axes not including the optical axis of primary electrons,
unevenness in illuminance of primary electrons in the area in which
primary electrons are applied to the sample is 10% or less, preferably 5%
or less, more preferably 3% or less, thus being very uniform. In this
case, the beam shape may be used even if the shape is not approximately
symmetric to two other orthogonal axes not including the optical axis of
primary electrons as described above.

[0509]In this embodiment, the sample W is irradiated with a plane beam
having the cross section formed into, for example, a rectangular shape of
200 μm×50 μm, thus making it possible to irradiate a small
area having a predetermined area on the sample W. To scan the sample W
with the plane beam, the sample W is placed on a high accuracy XY stage
(not shown) accommodating, for example, 300 mm wafer, and
two-dimensionally moved on the XY stage with the plane beam fixed.
Furthermore, since it is not necessary to concentrate primary electrons
onto a beam spot, the plane beam has a low current density, and the
sample W is not significantly damaged. For example, the current density
of the beam spot is 10 A/cm2 to 104 A/cm2 in the
conventional beam scanning defect inspection apparatus, while the current
density of the plane beam is only 0.0001 A/cm2 to 0.1 A/cm2 in
the defect inspection apparatus of FIG. 37. The current density is
preferably 0.001 A/cm2 to 1 A/cm2. The current density is more
preferably 0.01 A/cm2 to 1 A/cm2. On the other hand, the dose
is 1×10-5 C/cm2 in the conventional beam scanning system,
while it is 1×10-6 C/cm2 to 1×10-1 C/cm2
in the system of this embodiment, and the system of this embodiment has a
higher sensitivity. The dose is preferably 1×10-4 C/cm2
to 1×10-1 C/cm2, further preferably 1×10-3
C/cm2 to 1×10-1 C/cm2.

[0510]The incident direction of the primary electron beam is basically the
E direction of E×B 37•4, i.e. a direction of an electric
field, the integration direction of the TDI and the direction of movement
of the stage are made to match this direction. The incident direction of
the primary electron beam may be the B direction, i.e. a direction in
which a magnetic field is applied.

[0511]Secondary electrons, reflection electrons and back-scattered
electrons are generated from the area of the sample W irradiated with
primary electrons. First, for explanation of detection of secondary
electrons, secondary electrons emitted from the sample W are magnified by
the objective lens 37•6 and pass through the NA aperture plate
37•5 and the Wien filter 37•4 so as to travel in a direction
opposite to the second direction, and are then magnified again by an
intermediate lens 37•7, and further magnified by a projection lens
37•8 and enter a secondary electron detection system 37•9. In
the secondary optical system 37•9 guiding secondary electrons, the
objective lens 37•6, the intermediate lens 37•7 and the
projection lens 37•8 are all high accuracy electrostatic lenses,
and the magnification of the secondary optical system is variable.
Primary electrons are made to impinge on the sample W at almost a right
angle (±5 or less, preferably ±3 or less, more preferably ±1 or
less), and secondary electrons are taken out at almost a right angle, so
that shades by irregularities on the surface of the sample W never occur.

[0512]The Wien filter 37•4 is also called an E×B filter, has
an electrode and a magnet, has a structure in which the electric field is
orthogonal to the magnetic field, and has a function of bending primary
electrons at, for example, 35° to the sample direction (direction
perpendicular to the sample) while moving in a straight line at least one
of the secondary electron, the reflection electron and the back-scattered
electron from the sample.

[0513]The secondary electron detection system 37•9 receiving
secondary electrons from the projection lens 37•8 comprises a
micro-channel plate (MCP) 37•10 propagating incident secondary
electrons, a fluorescent screen 37•11 converting electrons leaving
the MCP 37•10 into light, and a sensor unit 37•12 converting
light leaving the fluorescent screen 37•11 into an electric signal.
The sensor unit 37•12 has a high sensitivity line sensor
37•13 comprised of a large number of solid imaging devices
two-dimensionally arranged, fluorescence emitted from the fluorescent
screen 37•11 is converted into an electric signal by the line
sensor 37•13, the electric signal is sent to an image processing
unit 37•14, and processed in parallel, in multistage and at a high
speed.

[0514]While the sample W is moved to have individual areas on the sample W
irradiated with a plane beam and scanned in order, the image processing
unit 37•14 accumulate data about the XY coordinates and images of
areas including defects one after another, and generate an inspection
result file including the coordinates and images of all areas of the
inspection object including defects for one sample. In this way,
inspection results can be collectively managed. When this inspection
result file is read, a defect distribution and a detailed defect list of
the sample are displayed on a display of the image processing unit 12.

[0515]Actually, of various kinds of components of the defect inspection
apparatus EBI, the sensor unit 37•12 is placed under an atmosphere,
but other components are placed in a column kept under vacuum, and
therefore in this embodiment, a light guide is provided on an appropriate
wall surface of the column, and light emitted from the fluorescent screen
37•11 is taken out into the atmosphere via the light guide and
passed to the line sensor 37•13.

[0516]Provided that the amount of electrons emitted from the sample W is
100%, the ratio of electrons that can reach the MCP 37•10
(hereinafter referred to as "transmittance") is expressed by the
following equation:

[0517]transmittance (%)=(amount of electrons that can reach MCP
37•10)/(amount of electrons emitted from sample W)×100. The
transmittance depends on the aperture area of the NA aperture plate
37•5. As an example, a relation between the transmittance and the
aperture diameter of the NA aperture plate is shown in FIG. 38. Actually,
at least one of the secondary electron, the reflection electron and the
back-scattered electron generated from the sample reach the electron
detection system D in the ratio of 200 to 1000 electrons per pixel.

[0518]The center of the image projected under magnification and formed on
the detector, and the center of the electrostatic lens are on a common
axis, the electron beam has the common axis as an optical axis between a
deflector and the sample, and the optical axis of the electron beam is
perpendicular to the sample.

[0519]FIG. 39 shows a specific example of the configuration of the
electron detection system 37•9 in the defect inspection apparatus
EBI of FIG. 37. A secondary electron image or reflection electron image
38•1 is formed on the incident surface of the MCP 37•10 by
the projection lens 37•8. The MCP 37•10 has, for example, a
resolution of 6 μm, a gain of 103 to 104, and 2100×520
active pixels, and propagates electrons according to the electron image
39•1 to irradiate the fluorescent screen 37•11. Consequently,
fluorescence is emitted from areas of the fluorescent screen 37•11
irradiated with electrons, and the emitted fluorescence is discharged
into the atmosphere via the light guide 39•2 of low deformation
(e.g. 0.4%). The discharged fluorescence is made to enter the line sensor
37•13 via an optical relay lens 39•3. For example, the
optical relay lens 39•3 has a magnification of 1/2, a transmittance
of 2.3%, and a deformation of 0.4%, and the line sensor 37•13 has
2048×512 pixels. The optical relay sensor 39•3 forms an
optical image 39•4 matching the electron image 39•1 on the
incident surface of the line sensor 37•1. An FOP (fiber optic
plate) may be used instead of the light guide 39•2 and the relay
lens 39•3, and the magnification in this case is 1. Furthermore, if
the number of electrons per pixel is 500 or greater, an MCP may be
omitted.

[0520]The defect inspection apparatus EBI shown in FIG. 37 can be operated
in one of a positive charge mode and a negative charge mode for secondary
electrons by adjusting an acceleration voltage of the electron gun
37•1 and a sample voltage applied to the sample W and using the
electron detection system 37•9. Further, by adjusting the
acceleration voltage of the electron gun 37•1, the sample voltage
applied to the sample W and objective lens conditions, the defect
inspection apparatus EBI can be operated in a reflection electron imaging
mode in which high energy reflection electrons emitted from the sample W
by irradiation of primary electrons is detected. The reflection electrode
has energy the same as the energy with which the primary electron enters
the sample W, and has a higher level of energy than that of the secondary
electron, and is therefore hard to be influenced by a potential by charge
of the sample surface or the like. For the electron detection system, an
electron impact detector such as an electron impact CCD or electron
impact TDI outputting an electric signal matching the intensity of
secondary electrons or reflection electrons may also be used. In this
case, the MCP 37•10, the fluorescent screen 37•11 and the
relay lens 39•3 (or FOP) are not used, but the electron impact
detector is installed at the imaging position and used. This
configuration enables the defect inspection apparatus EBI to operate in a
mode suitable for the inspection object. For example, the negative charge
mode or reflection electron imaging mode may be used to detect defects of
metal wiring, defects of gate contact (GC) wiring or defects of a resist
pattern, and the reflection electron imaging mode may be used to detect
poor conduction of a via or residues on the bottom of the via after
etching.

[0521]FIG. 40(A) illustrates requirements for operating the defect
inspection apparatus EBI of FIG. 37 in the above three modes. The
acceleration voltage of the electron gun 37•1 is VA, the
sample voltage applied to the sample W is VW, irradiation energy of
primary electrons when the sample is irradiated is EIN, and signal
energy of secondary electrons impinging upon the secondary electron
detection system 37•9 is EOUT. The electron gun 37•1 is
configured so that the acceleration voltage VA can be changed, the
variable sample voltage VW is applied to the sample W from an
appropriate power supply (not shown). Then, if the acceleration voltage
VA and the sample voltage VW are adjusted and the electron
detection system 37•9 is used, the defect inspection apparatus EBI
can operate in the positive charge mode in a range where a secondary
electron yield is greater than 1, and operate in the negative charge mode
in a range where the secondary electron yield is less than 1 as shown in
FIG. 40(B). Furthermore, by setting the acceleration voltage VA, the
sample voltage VW and the objective lens conditions, the defect
inspection apparatus EBI can use a difference in energy between the
secondary electron and the reflection electron to distinguish between the
two types of electrons, and thus can operate in the reflection electron
imaging mode in which only reflection electrons are detected.

[0522]One example of values of VA, VW, EIN and EOUT
for operating the defect inspection apparatus EBI in the reflection
electron imaging mode, the negative charge mode and the positive charge
mode will be described below.

[0535]As described above, principally, a fixed potential of 4 kV±10 V
(preferably 4 kV±1 V, more preferably 4 kV±10 V or less) is applied
as a potential VW for both the positive charge mode and negative
charge mode in the case of the secondary electron mode. On the other
hand, in the case of the reflection electron mode, the acceleration
potential VA is set to 4 kV±10 V (preferably 4 kV±1 V, more
preferably 4 kV±0.01 V or less), and the sample potential VW is
set to any potential lower than the acceleration potential of 4 kV or
less. In this way, secondary electrons or reflection electrons as a
signal impinge on the MCP as a detector with optimum energy of 4
keV±10 V 10 eV+α (preferably 4 keV±1 eV, more preferably 4
keV±0.01 eV).

[0536]The way of setting potentials described above corresponds
principally to the case where energy of signal electrons made to pass
through the secondary optical system is set to 4 keV, and an electron
image on the sample surface is formed on the detector, and by changing
this energy, the set potentials in the secondary electron mode and
reflection electron mode can be changed to obtain an electron image
appropriate to the type of sample. For the negative charge mode, an area
of electron irradiation energy lower than that of a positive charge area
of FIG. 40 (B) (e.g. 50 eV or less) can be used.

[0537]Actually, the detected amounts of secondary electrons and reflection
electrodes vary with surface compositions of inspected areas on the
sample W, pattern shapes and surface potentials. That is, the yield of
secondary electrons and the mount of reflection electrons vary depending
on the surface composition of the inspection object on the sample W, and
the yield of secondary electrons and the amount of reflection electrons
are greater in pointed areas or corners of the pattern than in plane
areas. Furthermore, if the surface potential of the inspection object on
the sample W is high, the amount of emitted secondary electrons
decreases. In this way, the intensities of electron signals obtained from
secondary electrons and reflection electrons detected by the detection
system 37•9 vary with the material, the pattern shape and the
surface potential.

2-3-3) E×B Unit (Wien Filter)

[0538]The Wien filter is a unit of an electromagnetic prism optical system
having an electrode and a magnetic pole placed orthogonally to each other
to orthogonalize an electric field and a magnetic field. If electric and
magnetic fields are selectively provided, an electron beam impinging
thereupon in one direction is deflected, and an electron beam impinging
in a direction opposite thereto can create conditions in which effects of
a force received from the electric field and a force received from the
magnetic field are offset (Wien conditions), whereby a primary electron
beam is deflected and applied onto a wafer at a right angle, and a
secondary electron beam can travel in a straight line toward a detector.

[0539]The detailed structure of an electron beam deflection unit of an
E×B unit will be described using FIG. 41 and FIG. 42 showing a
longitudinal plane along the A-A line of FIG. 41. As shown in FIG. 41, a
field of an electron beam deflection unit 41•2 of an E×B unit
41•1 has a structure in which an electric field and a magnetic
field are orthogonalized in a plane perpendicular to the optical axis of
a projection optical unit, i.e. E×B structure. Here, the electric
field is generated by electrodes 41•3 and 41•4 each having a
concave curved surface. The electric field generated by the electrodes
41•3 and 41•4 is controlled by control units 41•5 and
41•6, respectively. On the other hand, electromagnetic coils
41•7 and 41•8 are placed in such a manner that they are
orthogonal to the electrodes 41•3 and 41•4 for generating
electric fields, whereby magnetic fields are generated. Furthermore, the
electrodes 41•3 and 41•4 for generating electric fields is
point-symmetric, but they may be concentric.

[0540]In this case, to improve uniformity of the magnetic field, pole
pieces having parallel and plain shapes are provided to form a magnetic
path. The behavior of the electron beam in the longitudinal plane along
the A-A line is as shown in FIG. 42. Applied electron beams 42•1
and 42•2 are deflected by electric fields generated by the
electrodes 41•3 and 41•4 and magnetic fields generated by
electromagnetic coils 41•7 and 41•8, and then enter the
sample surface at a right angle.

[0541]Here, the position and angle at which the irradiation electron beams
42•1 and 42•2 enter the electron beam deflection unit
41•2 are uniquely determined when energy of electrons is
determined. Further, control units 41•5, 41•6, 41•9 and
41•10 control electric fields generated by the electrodes
41•3 and 41•4 and magnetic fields generated by the
electromagnetic coils 41•7 and 41•8 so that secondary
electrons 42•3 and 42•4 travel in a straight line, i.e. the
requirement for the electric field and magnetic filed of v×B=E is
met, whereby secondary electrons travel in straight line through the
electron beam deflection unit 41•2, and impinge on the projection
optical system. Here, v represents the speed of the electron (m/s), B
represents the magnetic field (T), e represents the amount of electric
charge (C), and E represents the electric field (V/m).

[0542]Here, the E×B filter 41•1 is used for separation of
primary electrons and secondary electrons, but the magnetic field can be
used for the separation as a matter of course. Furthermore, only the
electric field may be used to separate primary electrons and secondary
electrons. Further, it may be used to separate primary electrons and
reflection electrons as a matter of course.

[0543]Now, as the embodiment 9, an alteration example of the E×B
filter will be described with reference to FIG. 43. FIG. 43 is a
sectional view taken along a plane perpendicular to the optical axis.
Four pairs of electrodes 43•1 and 43•2, 43•3 and
43•4, 43•5 and 43•6, and 43•7 and 43•8 for
generating electric fields are formed by a nonmagnetic conductive
material, are cylindrical as a whole, and are fixed with screws (not
shown) on the inner surface of an electrode supporting barrel 43•9
made of insulating material, or the like. The axis of the electrode
supporting barrel 43•9 and the axis of the cylinder formed by
electrodes are made to match an optical axis 43•10. A groove
43•11 parallel to the optical axis 43•10 is provided on the
inner surface of the electrode supporting barrel 43•9 between the
electrodes 43•1 to 43•8. The area of the inner surface is
coated with a conductive material 43•12, and set at an earth
potential.

[0544]If a voltage proportional to "cos θ1" is given to the
electrodes 43•3 and 43•5, a voltage proportional to "-cos
θ1" is given to the electrodes 43•6 and 43•4, a voltage
proportional to "cos θ2" is given to the electrodes 43•1 and
43•7, and a voltage proportional to "-cos θ2" is given to the
electrodes 43•8 and 43•2 when electric fields are generated,
almost uniform parallel electric fields can be obtained in an area
equivalent to about 60% of the inner diameter of the electrode. The
results of simulation of an electric filed distribution are shown in FIG.
44. Furthermore, four pairs of electrodes are used in this example, but
uniform parallel electric fields can be obtained in an area equivalent to
about 40% of the inner diameter even if a three pairs of electrodes are
used.

[0545]Generation of magnetic fields is performed by placing two
rectangular platinum alloy permanent magnets 43•13 and 43•14
in parallel outside the electrode supporting barrel 43•9. A raised
portion 43•16 composed of a magnetic material is provided around
the surfaces of the permanent magnets 43•13 and 43•14 on the
optical axis 43•10 side. This raised portion 43•16
compensates for outward convex deformation of a magnetic line of flux on
the optical axis side 43•10, and its size and shape can be
determined by simulation analysis.

[0546]A yoke or magnetic circuit 43•15 made of ferromagnetic
material is provided outside the permanent magnets 43•13 and
43•14 so that a channel situated opposite to the optical axis
43•10 of the magnetic line of flux by the permanent magnets
43•13 and 43•14 forms a barrel concentric with the electrode
supporting barrel 43•9.

[0547]An E×B separator shown in FIG. 43 may be applied not only to
the projection type electron beam inspection apparatus shown in FIG. 25-1
but also to a scanning electron beam inspection apparatus.

[0548]One example of the scanning electron beam inspection apparatus is
shown in FIG. 25-2. An electron beam is applied from an electron gun
25•14 to a sample 25•15. A primary system electron beam
passes through an E×B 25•16, but travels in a straight line
with no deflection force exerted thereon at the time of incidence, is
focused by an objective lens 25•17, and enters the sample
25•15 at almost a right angle. Electrons exiting from the sample
25•15 are guided to a detector 25•18 with a deflection force
exerted thereon by the E×B 25•16. In this way, by adjusting
an electric field and a magnetic field of the E×B 25•16, one
of charged particle beams of the primary system and the secondary system
can be made to travel in a straight line, with the other traveling in a
straight line in any direction.

[0549]Furthermore, if the E×B 25•16 is used, the deflection
force is exerted to cause an aberration in a direction of deflection, and
therefore an E×B deflector may be further provided between the
electron gun 25•14 of the primary system optical system and the
E×B 25•16 for correcting the aberration. Furthermore, for the
same purposes, the E×B detector may be further provided between the
detector 25•18 of the secondary system and the E×B
25•16.

[0550]In the scanning electron beam inspection apparatus or scanning
electron microscope, finely focusing with the primary system electron
beam leads to an improvement in resolution and therefore generally, the
primary system electron beam is made to travel in a straight line as
shown in FIG. 25•2 with no excessive reflection force exerted on
the primary electron beam, and the secondary beam is deflected. However,
if conversely, it is more preferable that the primary beam is deflected
and the secondary beam is made to travel in a straight line, such a
configuration may be adopted. Similarly, in the projection type electron
beam inspection apparatus, it is generally preferable that a deflection
force causing no aberration is not given to the secondary beam to match
imaging areas on the sample with pixels on a CCD of the detector. Thus,
generally, the primary beam is deflected and the secondary beam is made
to travel in a straight line as shown in FIG. 25-1, but if it is more
preferable that the primary beam is made to travel in a straight line and
the secondary beam is deflected, such a configuration may be adopted.

[0551]Furthermore, the intensities of the electric field and the magnetic
field of E×B may be set differently for each mode of the secondary
electron mode and the reflection electron mode. The intensities of the
electric field and the magnetic field can be set so that an optimum image
can be obtained for each mode. When it is not required that the set
intensity should be changed, the intensity may be kept a constant level
as a matter of course.

[0552]As apparent from the above description, according to this example,
both the electric field and magnetic field can take uniform areas
sufficiently around the optical axis, and the irradiation range of the
primary electron beam is expanded, the aberration of the image made to
pass the E×B separator can be kept at an uninfluential level.
Furthermore, since the raised portion 43•16 is provided in the
periphery of the magnetic pole forming the magnetic field, and the
magnetic pole is provided outside an electric field generating electrode,
a uniform magnetic field can be generated, and deformation of the
electric field by the magnetic pole can be reduced. Furthermore, since a
permanent magnet is used to generate the magnetic field, the overall
E×B separator can be contained in a vacuum. Further, the electric
field generating electrode and a magnetic path forming magnetic circuit
have concentric cylindrical shapes having an optical axis as a central
axis, whereby the overall E×B separator can be downsized.

2-3-4) Detector

[0553]A secondary electron image from a wafer, which is formed in the
secondary optical system, is first amplified by a micro-channel plate
(MCP), then enters a fluorescent screen, and is converted into an optical
image. As principle of the MCP, several millions to several tens of
millions of very slender conductive glass capillaries each having a
diameter of 1 to 100 μm and a length of 0.2 to 10 mm, preferably a
diameter of 2 to 50 μm and a length of 0.2 to 5 mm, more preferably a
diameter of 6 to 25 μm and a length of 0.24 to 1.0 mm are bundled
together to form a thin plate, and by applying a predetermined voltage
thereto, each of capillaries acts as an independent secondary electron
amplifier, and a secondary electron amplifier is formed as a whole. The
image converted into light by this detector is projected on the TDI-CCD
in a ratio of 1:1 in an FOP system placed under the atmosphere via a
vacuum transparent window.

[0554]Now, the operation of the electro-optical apparatus having the
configuration described above will be described. As shown in FIG. 25-1, a
primary electron beam emitted from the electron gun 25•4 is
converged by the lens system 25•5. The converged primary electron
beam is made to enter the E×B-type deflector 25•6, deflected
so as to irradiate the surface of the wafer W at a right angle, and made
to form an image on the surface of the wafer W by the objective lens
system 25•8.

[0555]Secondary electrons emitted from the wafer by irradiation of the
primary electron beam are accelerated by the objective lens 25•8,
enters the E×B-type deflector 25•6, and travels though the
deflector in a straight line, and is guided through the lens system
25•10 of the secondary optical system to the detector 25•11.
The secondary electrons are then detected by the detector 25•11,
and a detection signal thereof is sent to the image processing unit
25•12. Furthermore, a high voltage of 10 to 20 kV is applied to the
objective lens 25•7, and the wafer is placed.

[0556]Here, if the wafer W has the via 25•13, the electric field of
the electron beam irradiation surface of the wafer is 0 to -0.1 V/mm (-
indicates a high potential at the wafer W side) provided that the voltage
given to the electrode 25•8 is -200 V. In this state, no discharge
occurs between the objective lens system 25•7 and the wafer W, and
the defect inspection for the wafer W can be performed, but efficiency of
detection of secondary electrons is slightly reduced. Thus, a series of
operations for irradiating an electron beam to detect secondary electrons
are carried out, for example, four times, the obtained detection results
of the four time operations are subjected to processing such as
cumulative addition and averaging to obtain a predetermined detection
sensitivity.

[0557]Furthermore, when the wafer has no via 25•13, no discharge
occurs between the objective lens 25•7 and the wafer, and defect
inspection for the wafer can be performed even if the voltage given to
the electrode 25•8 is +350 V. In this case, secondary electrons are
converged by the voltage given to the electrode 25•8, and are
further converged by the objective lens 25•7, and thus efficiency
of detection of secondary electrons in the detector 25•11 is
improved. Accordingly, the speed of processing as a wafer defect
apparatus is enhanced, and inspection can be carried out in high
throughput.

2-3-5) Power Supply

[0558]A power supply unit of the apparatus is mainly comprised of a direct
current high voltage precision power supply having about several hundreds
output channels for control of electrodes, and has its supply voltage
varied depending on the role of the electrode and the positional
relation. In view of demands on resolution and accuracy of images, the
power supply unit is required to have stability in the order of several
100 ppm or less, preferably 20 ppm or less, more preferably several ppm
or less with respect to the set value. To minimize variations of the
voltage with time and temperature, noise ripples and the like as factors
impairing stability, and some contrivance is made for a circuit system,
selection of parts and implementation.

[0559]Types of power supplies other than electrodes include a heating
constant current source for a heater, a high-voltage and high-speed
amplifier for two-dimensionally deflecting a beam to confirm aligning of
the beam near the center of an aperture electrode when the primary beam
is centered, a heating constant current source for a heater, a constant
current source for an electromagnetic coil for E×B as an energy
filter, a retarding power supply for applying a bias to a wafer and a
power supply generating a potential for adsorbing a wafer to an
electrostatic chuck, a high-voltage and high-speed amplifier for making
an EO (electron optical) correction, and an MCP power supply amplifying
electrons with principle of a photomultiplier.

[0560]FIG. 45 shows the overall configuration of the power supply unit. In
this figure, an electric power is supplied to an electrode of a column
portion 45•1 through a connection cable from a power supply rack
45•2 and high-speed and high-voltage amplifiers 45•3,
45•4 and 45•5, although not shown in the figure. The
high-speed and high-voltage amplifiers 45•3 to 45•5 are
broadband amplifiers, and deal with signals of high frequencies (DC-MHz),
and therefore they are placed near the electrode to prevent an increase
in electrostatic capacity of a cable in order to inhibit property
degradation and an increase in power consumption due to the electrostatic
capacity of the cable. An correction signal is outputted from an EO
correction 45•6, and converted into an voltage having a phase and a
magnitude matching a vector value for each electrode of an octupole at an
octupole conversion unit 45•7, and the voltage is inputted to the
high-speed and high-voltage amplifier 45•4, amplified, and then
supplied to an electrode included in a column.

[0561]An AP image acquisition block 45•8 has a role as an auxiliary
function such that a serrate wave is generated from the AP image
acquirement block 45•8 to ensure centering of a beam near the
center of an aperture electrode when a primary beam is centered, and
applied to a deflection electrode of the column portion 45•1 by the
high-speed and high-voltage amplifier. The beam is two-dimensionally
deflected, whereby the magnitude of a beam current received at the
aperture electrode is related to the position, and an image is displayed
to set the beam position to the mechanical central position.

[0562]An AF control 46•9 achieves a function such that a voltage
corresponding to the best focal condition measured in advance is stored
in a memory, the value of the voltage is read according to the stage
position, the voltage is converted into an analog voltage by a D/A
converter, the voltage is applied a focus adjustment electrode included
in the column portion 45•1 through the high-speed and high-voltage
amplifier 45•5, and an observation is made while maintaining the
optimum focus position.

[0563]The direct current high voltage precision power supply having about
several hundreds output channels for control of voltages, comprised of
power supply groups 1 to 4, is housed in the power supply rack
45•2. The power supply rack 45•2 constitutes a system capable
of receiving commands from a CPU unit 45•13 by means of a
communication card 45•11, an optical fiber communication
45•12 having electric insulation quality to ensure safety and
prevent occurrence of a grand loop to prevent entrance of noises, and the
like, by a control communication unit 45•10, and sending a status
such as abnormality of power supply apparatus. A UPS 45•14 prevents
destruction of apparatus, abnormal discharges, risks to human bodies and
the like caused by overrunning of the system when control abnormality
occurs due to service interruption and unexpected power blockage. A power
supply 45•15 is a power reception unit of the main body, and is
configured so that safety cooperation can be achieved as an overall
inspection apparatus including interlock, current limitation and the
like.

[0564]The communication card 45•11 is connected to a data bus
45•16 and an address bus 45•17 of the control CPU unit
45•13, so that real time processing can be carried out.

[0565]FIG. 46 shows one example of the circuit configuration of a static
high voltage unipolar power supply (for lens) for a circuit system where
a static DC of several hundreds to several tens kilovolts is produced. In
FIG. 46, a signal source 46•1 is caused to generate an alternating
current voltage having a frequency providing an optimum magnetic
permeability of a trans 46•2, and the voltage is made to pass
through a multiplier 46•3, and then guided to a drive circuit
46•4 to generate a voltage having an amplitude several tens to
several hundreds times greater by the trans 46•2. A cock craft
walten circuit 46•5 is a circuit increasing a voltage while
performing rectification. By combination of the trans 46•2 and the
cock craft walten circuit 46•5, a desired DC voltage is obtained,
and by a low pass filter 56•6, further flatness is achieved to
reduce ripples and noises. A high-voltage output is divided according to
the resistance ratio of output voltage detection resistances 46•7
and 46•8 to obtain a voltage within a range of voltages capable of
being dealt with by a usual electronic circuit. Because stability of this
resistance mostly determines voltage accuracy, elements excellent in
temperature stability, long term variations and the like are used, and in
view of the fact that the division ratio is especially important,
measures are taken such that a thin film is formed on the same insulation
substrate, or resistance elements are brought into close contact with one
another so that the temperature does not vary.

[0566]The result of the division is compared to the value of a reference
voltage generating D/A converter 46•10 by a calculation amplifier
46•9, and if there is a difference, the output of the calculation
amplifier 46•9 is increased or decreased, and an AC voltage having
an amplitude matching the value thereof is outputted from the multiplier
46•3 to form a negative feedback. Although not shown in the figure,
the output of the calculation amplifier 46•9 is made to be
unipolar, or the quadrant of response of the multiplier 46•3 is
limited to prevent saturation. The calculation amplifier 46•9
requires a very large amplification gain (120 dB or greater), and is
mostly used in an open loop as an element, and therefore a low noise
operation amplifier is used. The reference voltage generating D/A
converter 46•10 requires stability equivalent to or higher than
that of the output voltage detection resistances 46•7 and
46•8 in terms of accuracy. To generate this voltage, a reference IC
having a constant voltage diode using a hand gap combined with a
thermostabilization feature using a heater (not shown) is often used, but
a Peltier element is used instead of the heater so that thermostability
can be further improved. Furthermore, the Peltier element may be used in
a single or multi-stage for thermostabilization of the output voltage
detection resistances 46•7 and 46•8.

[0567]FIG. 47 shows one example of the circuit configuration of a static
bipolar power supply (for aligner or the like). The basic concept is such
that V5 and V6 are generated with a power supply equivalent to that of
the circuit of FIG. 46, and the voltages are used to input command values
from a component 47•1 to a linear amplifier constituted by
components 47•1 to 47•6 to form a bipolar high-voltage power
supply. Generally, the calculation amplifier 47•2 operates at
around ±12 V, and therefore although not shown in the figure,
amplification circuits by discrete elements are required between the
component 47•2 and the components 47•5 and 47•6 to
amplify the voltage from +several volts to ± several hundreds to
several thousands volts. Notices about characteristics required for the
components 47•1 to 47•4 are the same as those described with
the circuit of FIG. 46.

[0568]FIGS. 48 to 50 each show an example of a circuit of a special power
supply, and FIG. 48 shows an example of a circuit for a heater and a gun,
which is constituted by components 48•1 to 48•4. A voltage
source 48•1, a resistance 48•3 and a power supply 48•4
are superimposed on a bias voltage source 48•2. The power supply
48•4 for a heater is constituted by a constant current source, the
value of an actually passing current is detected by the resistance
48•3, and although not shown in the figure, the value is
temporarily digitized, isolated with optical fibers or the like, and sent
to the control communication unit 45•10. For the setting of the
voltage value of the voltage source 48•1, the current value of the
power supply 48•4 and the like, the value from the control
communication unit 45•10 is inversely converted in the same
principle, and the value is set for an actual power setting unit.

[0569]FIG. 49 shows an example of a power supply circuit for an MCP, which
is comprised of voltage sources 49•1 and 49•2, relay circuits
49•3 and 49•4, and current detection circuits 49•5,
49•6 and 49•7. A terminal MCP1 makes measurements from
several Pas for measurement of the value of a current passing into the
MCP, and is thus required to have a strict shield structure to prevent
entrance of leaked currents and noises. A terminal MCP2 includes current
measurement after amplification by the MCP, and can calculate an
amplification gain from the ratio of values of currents passing through
the resistances 49•6 and 49•7. The resistance 49•5
measures a current on a fluorescent screen. Measurement and setting at
the superimposed portion are the same as those at the heater and gun.

[0570]FIG. 50 shows an example of a circuit of a constant current source
for an E×B magnetic field coil constituted by components 50•1
and 50•2, which generally outputs a current of several hundred mA.
Stability of the magnetic field as an energy filter is important, and
stability in the order of several ppm is required.

[0571]FIG. 51 shows one example of a power supply for a retarding and
electrostatic chuck, which is constituted by components 51•1 to
51•9. A power supply similar to the static bipolar power supply
(for aligner) of FIG. 46 is superimposed on a bias power supply (for
retarding) 51•10. Measurement and setting at the superimposed
portion are the same as those at the heater and gun (FIG. 48).

[0572]FIG. 52 shows one example of the hardware configuration of an EO
correcting deflection electrode, which is constituted by components
52•1 to 52•7. An correction signal is inputted to an octupole
conversion unit 52•4 from an X axis EO correction 52•1 and a
Y axis EO correction 52•2, and an output after conversion is sent
to a high-speed amplifier 52•5. The voltage is amplified from
several tens of volts to several hundreds of volts by the high-speed
amplifier 52•5, and then applied to EO correction electrodes
52•6 situated at angular intervals of 45°. A ΔX
correction 52•3 is an input for fine correction such as correction
of mirror bend, and is added to an X signal within the octupole
conversion unit 52•4.

[0573]FIG. 53 shows one example of the circuit configuration of the
octupole conversion unit, which performs vector operation from signals
53•2, 53•3, 53•4 and 53•5 for electrodes
53•1 situated at angular intervals of 45° other than X and Y
axes, and generate equivalent voltages. The example of operation in this
case uses values described at components 53•6, 53•7,
53•8 and 53•9. This can be achieved by an analog resistance
network, or read of the table by a ROM when components 53•6 to 53.9
are digital signals.

[0574]FIG. 54 shows one example of a high-speed and high voltage
amplifier, which is constituted by components 54•1 to 54•11.
An example of a waveform during output of a short wave is shown in FIG.
54(B). In this example, Power Operation Amplifier PA 85A manufactured by
APEX Co., Ltd. (U.S.A) is used to form an amplifier, and a bandwidth
covering a mega-band, an output range of about ±200 V, and a through
rate larger than about 1000 V/μs can be achieved, thus achieving
dynamic characteristics required for the high-speed and high-voltage
amplifier.

2-4) Precharge Unit

[0575]As shown in FIG. 13, the precharge unit 13•9 is placed in
proximity to the column 13•38 of the electro-optical apparatus
13•8 in the working chamber 13•16. This inspection apparatus
is a type of apparatus irradiating an electron beam to a substrate as an
inspection object, i.e. a wafer to inspect a device pattern or the like
formed on the wafer surface, and therefore information of secondary
electrons or the like generated by irradiation of the electron beam is
used as information of the wafer surface, but the wafer surface may be
charged (charge-up) depending on conditions of a wafer material, energy
of irradiation electrons and the like. Further, strongly charged sites
and weakly charged sites may appear on the wafer surface. Unevenness in
charge amount on the wafer surface causes unevenness in information of
secondary electrons, thus making it impossible to obtain precise
information.

[0576]Thus, in the embodiment of FIG. 13, a precharge unit 13•9
having a charged particle irradiation unit 13•39 is provided to
prevent such unevenness. Before inspection electrons are directed to
predetermined sites of the wafer to be inspected, charged particles are
irradiated from the charged particle irradiation unit 13•39 of the
precharge unit 13•9 to eliminate charge unevenness. For the
charge-up on the wafer surface, an image on the wafer surface as an
inspection object is formed in advance, and the image is evaluated to
perform detection, and the precharge unit 13•9 is operated based on
the detection. Furthermore, in this precharge unit 13•9, the focus
of a primary electron beam may be shifted, i.e. the beam shape may be
blurred to irradiate the wafer.

[0577]FIG. 55 shows main parts of the first embodiment of the precharge
unit 13•9. Charged particles 55•1 are applied from a charged
particle irradiation beam source 55•2 to the sample substrate W
while being accelerated by a voltage set by a bias power supply
55•3. An inspection subject area 55•4 is an area already
subjected to charged particle irradiation as preprocessing together with
an area 55•5. An area 55•6 is one being irradiated with
charged particles. In this figure, the sample substrate W is scanned in a
direction shown by an arrow in the figure, but if the sample substrate W
is scanned to and fro, another charged particle beam source 55•7 is
placed on the opposite side of a primary electron beam source, and the
charged particle beam sources 55•2 and 55•7 are turned on and
off alternately in synchronization with the scan direction of the sample
substrate W as shown by a dotted line in the figure. In this case, if
energy of charged particles is too high, the yield of secondary electrons
from an insulation portion of the sample substrate W exceeds 1, and thus
the surface is positively charged, and even if the yield is 1 or less,
the phenomenon is implicated if secondary electrons are generated to
reduce irradiation efficiency, and therefore it is effective to set the
voltage to a landing voltage of 100 eV or less (ideally a voltage of 0 eV
to 30 eV) at which generation of secondary electrons is rapidly reduced.

[0578]FIG. 56 shows the second embodiment of the precharge unit
13•9. In this figure, a type of irradiation beam source irradiating
an electron beam 56•1 as a charged particle beam is shown. The
irradiation beam source is comprised of a hot filament 56•2, an
anode electrode 56•3, a shield case 56•4, a filament power
supply 56•5 and an anode power supply 56•6. The anode
56•3 is provided with a slit having a thickness of 0.1 mm, a width
of 0.2 mm and a length of 1.0 mm, and the positional relation between the
anode 56•3 and the filament (thermal electron emission source)
56•2 is a form of a three-pole electron gun. The shield case
56•4 is provided with a slit having a width of 1 mm and a length of
2 mm, and is situated at a distance of 1 mm from the anode 56•3,
and is assembled so that the slit centers of the shield case 56•4
and the anode 56•3 match each other. The material of the filament
is tungsten (W), which is current-heated at 2 A, so that an electron
current of several microamperes is obtained at an anode voltage of 20 V
and a bias voltage of 30 V.

[0579]The example shown here is only one example and, for example, the
material of the filament (thermal electron emission source) may be a
metal having a high melting point such as Ta, Ir or Re, thoria coat W, an
oxide cathode or the like, and the filament current varies depending on
the material, the line diameter and the length as a matter of course.
Furthermore, other types of electron guns can be used as long as
appropriate values can be set for the electron beam irradiation area, the
electron current and energy.

[0580]FIG. 57 shows the third embodiment of the precharge unit 13•9.
A type of irradiation beam source irradiating ions 57•1 as a
charged particle beam is shown. This irradiation beam source is comprised
of a filament 57•2, a filament power supply 57•3, an emission
power supply 57•4 and an anode shield case 57•5, and an anode
57•6 and the shield case 57•5 are provided with slits having
the same size of 1 mm×2 mm, and are assembled so that the centers
of both slits match each other at intervals of 1 mm. Ar gas 57•8 is
introduced up to about 1 pa into the shield case 57•5 through a
pipe 57•7, and the shield case 57•5 is operated in an arc
discharge type by the hot filament 57•2. The bias voltage is set to
a positive value.

[0581]FIG. 58 shows the case of a plasma irradiation process as the fourth
embodiment of the precharge unit 13•9. Its structure is the same as
that of FIG. 57. It is operated in an arc discharge type by the hot
filament 57•2 in the same manner as described above, but by setting
the bias voltage to 0 V, plasma 58•1 is leaked through the slit by
a gas pressure and applied to the sample substrate. In the case of plasma
irradiation, both positive and negative surface potentials on the surface
of the sample substrate can be brought close to 0 because of the group of
particles having both positive and negative charges compared to other
processes.

[0582]The charged particle irradiation unit placed in proximity to the
sample substrate W has a structure shown in FIGS. 55 to 58. In those
figures, charged particles 55•1 are irradiated under appropriate
conditions so that the surface potential is 0 for a difference in surface
structure of the sample substrate, such as an oxide film and a nitride
film and each of sample substrates in different fabrication steps. After
the sample substrate is irradiated under optimum irradiation conditions,
i.e. the potential of the surface of the sample substrate W is equalized
or neutralized with charged particles, an image is formed with electron
beams 55•8 and 55•9 and defects are detected.

[0583]As described above, in this embodiment, deformation of a measurement
image with charge does not occur or deformation is very little if any
owing to processing just before measurement by irradiation of charged
particles, thus making it possible to measure defects correctly.
Furthermore, since the stage can be scanned by application of a large
current (e.g. 1 μA to 20 μA, preferably 1 μA to 10 μA, more
preferably 1 μA to 5 μA), which has caused problems if used, a
large amount of secondary electrons are emitted from the surface of the
wafer, and therefore a detection signal having a good S/N ratio (e.g. 2
to 1000, preferably 5 to 1000, more preferably 10 to 100) is obtained,
resulting in an improvement in reliability of defect detection.
Furthermore, because of the high S/N ratio, satisfactory image data can
be created even if the stage is scanned at a higher speed, thus making it
possible to increase throughput of inspection.

[0584]FIG. 59 schematically shows an imaging apparatus comprising the
precharge unit according to this embodiment. This imaging apparatus
59•1 comprises a primary optical system 59•2, a secondary
optical system 59•3, a detection system 59•4, and charge
controlling means 59•5 for equalizing or reducing charges with
which an imaging object is electrified. The primary optical system
59•2 is an optical system irradiating an electron beam to an
inspection object W (hereinafter referred to as object), and comprises an
electron gun 59•6 emitting electron beams, an electrostatic lens
59•8 collecting a primary electron beam 59•7 emitted from the
electron gun 59•6, a Wien filter or E×B deflector 59•9
deflecting the primary electron beam so that its optical axis is
perpendicular to the surface of the object, and an electrostatic lens
59•10 collecting the electron beam. They are placed in descending
order with the electron gun 59•6 situated at the uppermost
position, and in such a manner that the optical axis of the primary
electron beam 59•7 emitted from the electron gun is slanted with
respect to a line vertical to the surface of the object W (sample
surface), as shown in FIG. 59. The E×B deflector 59•9 is
comprised of an electrode 59•11 and an electromagnet 59•12.

[0585]The secondary optical system 59•3 comprises an electrostatic
lens 59•3 placed on the upper side of the E×B deflector
49•9 of the primary optical system. The detection system 59•4
comprises a combination 59•15 of a scintillator and a micro-channel
plate (MCP) converting secondary electrons 59•14 into a light
signal, a CCD 59•16 converting the light signal into an electric
signal, and an image processing apparatus 59•17. The structure and
the function of the primary optical system 59•2, the secondary
optical system 59•3 and the detection system 59•4 are the
same as those of the conventional technique, and therefore detailed
descriptions thereof are not presented.

[0586]In this embodiment, the charge controlling means 59•5 for
equalizing or reducing charges with which the object is electrified
comprises an electrode 59•18 placed close to the object W between
the object W and the electrostatic lens 59•10 of the primary
optical system 59•2 closest to the object W, a changeover switch
59•19 electrically connected to the electrode 59•18, a
voltage generator 59•21 electrically connected to one terminal
59•20 of the changeover switch 59•19, and a charge detector
59•23 electrically connected to the other terminal 59•22 of
the changeover switch 59•19. The charge detector 59•23 has a
high impedance. The charge reducing means 59•5 further comprises a
grid 59•24 placed between the electron gun 59•6 of the
primary optical system 59•2 and the electrostatic lens 59•8,
and a voltage generator 59•25 electrically connected to the grid
59•24. A timing generator 59•26 indicates operation timing to
the CCD 59•16 and image processing apparatus 59•17 of the
detection system 59•4, the changeover switch 59•19 of the
charge reducing means 59•5, the voltage generator 59•21 and
the charge detectors 69•23 and 59•25.

[0587]The operation of the electron beam apparatus having the
configuration described above will now be described. The primary electron
beam 59•7 emitted from the electron gun 59•6 passes through
the electrostatic lens 59•8 of the primary optical system
59•2 to reach the E×B deflector 59•9, and is deflected
so as to be perpendicular to the surface (object surface) WF of the
object W by the E×B deflector 59•9, and applied to the
surface of the object W through the electrostatic lens 59•10. The
secondary electrons 59•14 are emitted from the surface WF of the
object W according to properties of the object. The secondary electrons
59•14 are sent through the electrostatic lens 59•13 of the
secondary optical system 59•3 to the combination 59•15 of a
scintillator and an MCP of the detection system 59•4, and converted
into light by the scintillator, the light is subjected to photoelectric
conversion by the CCD 59•16, and the converted electric signal
causes the image processing apparatus 59•17 to form a
two-dimensional image (having a gray scale). Furthermore, as in the case
of this normal type of inspection apparatus, the primary electron beam to
be irradiated to the object can be applied to entire required sited on
the object surface WF to collect data of the object surface by scanning
the primary electron beam with well known deflecting means (not shown),
or moving a table T supporting the object in the two-dimensional
direction of X and Y, or by combination thereof.

[0588]A charge is generated near the surface of the object W with the
primary electron beam 59•7 applied to the object W, and the object
W is positively charged. As a result, the secondary electrons 59•14
generated from the surface WF of the object W have the path changed
according to the situation of the charge by the Coulomb force. As a
result, the image formed in the image processing apparatus 59•17 is
deformed. The charge of the object surface WF varied with the properties
of the object W, and therefore if the wafer is used as an object, the
charge is not the same on the same wafer, and varies with time. Thus,
when patterns at two sites on the wafer are compared, defect detection
may occur.

[0589]Thus, in this embodiment according to the present invention,
utilizing spare time after the CCD 59•16 of the detection system
59•4 captures an image equivalent to one scan, the charge amount of
the electrode 59•18 placed near the object W is measured by the
charge detector 59•23 having a high impedance. A voltage for
irradiating electrons appropriate to the measured charge amount is
generated by the voltage generator 59•21, the changeover switch
59•19 is operated to connect the electrode 59•18 to the
voltage generator 59•21 after the measurement, and the voltage
generated by the voltage generator is applied to the electrode
59•18 to offset the charge. In this way, no deformation occurs in
the image formed in the image processing apparatus 59•17.
Specifically, when a usual voltage is given to the electrode 59•18,
a converged electron beam is applied to the object W, but if a different
voltage is given to the electrode 59•18, focusing conditions are
significantly shifted, a large area expected to be charged is irradiated
in a small current density, and the positive charge of the positively
charged object is neutralized, whereby the voltage of the large area
expected to be charged can be equalized to a specific positive (negative)
voltage, or the charge is equalized and reduced, whereby a lower positive
(negative) voltage (including zero volt) can be achieved. The operation
for offsetting the charge is carried out for each scan.

[0590]The Wenelt electrode or grid 59•24 has a function to stop the
electron beam applied from the electron gun 59•6 in timing of spare
time so that the measurement of the charge amount and the operation for
offsetting the charge are carried out with stability. Timing of the above
operation, which is indicated by the timing generator 59•26, is for
example timing shown in the timing chart of FIG. 60. Furthermore, if the
wafer is used as an object, the charge amount varies depending on the
position of the wafer, and therefore a plurality of pairs of electrodes
59•18, changeover switches 59•19, voltage generators
59•21 and charge detectors 59•23 can be provided in the
scanning direction of the CCD and fractionalized to perform more accurate
control.

[0591]According to this embodiment, the following effects can be
exhibited.

[0592](1) Deformation of the image occurring due to charge can be reduced
irrespective of the properties of the inspection object.

[0593](2) Because charge is equalized and offset utilizing spare time in
measurement time in the conventional process, the throughput is not
affected at all.

[0594](3) Because processing can be carried out in real time, time for
post-processing, a memory and the like are not required.

[0595](4) Observation of the image and detection of defects can be
performed at a high speed and with high accuracy.

[0596]FIG. 61 shows the outlined configuration of a defect inspection
apparatus comprising a precharge unit according to another embodiment of
the present invention. This defect inspection apparatus comprises the
electron gun 59•6 emitting a primary electron beam, the
electrostatic lens 59•8 deflecting and shaping the emitted primary
electron beam, a sample chamber 61•1 capable of being evacuated by
a pump (not shown), a stage 61•2 situated in the sample chamber and
capable of moving in a horizontal plane with a sample such as a
semiconductor wafer W placed thereon, the electrostatic lens 59•13
of a projection system map-projecting a secondary electron beam and/or a
reflection electron beam emitted from the wafer W by irradiation of the
primary electron beam under predetermined magnification to form an image,
a detector 61•3 detecting the formed image as a secondary electron
image of the wafer, and a control unit 61•4 controlling the entire
apparatus and detecting defects of the wafer W based on the secondary
electron image detected by the detector 61•3. Furthermore, not only
secondary electrons but also reflection electrons contribute to the
secondary electron image described above, but the image is referred to as
a secondary electron image herein.

[0597]In the sample chamber 61•1, a UV lamp 61•5 emitting a
light beam in a wave range including ultraviolet light is placed above
the wafer W. The glass surface of this UV lamp 61•5 is coated with
a photoelectron emission material 61•6 emitting photoelectrons
e.sup.- resulting from a photoelectronic effect by the light beam emitted
from the UV lamp 61•5. The UV lamp 61•5 may be any light
source emitting a light beam in a wave range having a capability of
emitting photoelectrons from the photoelectron emission material
61•6. Generally, a low pressure mercury lamp emitting ultraviolet
light of 254 nm is advantageous in terms of a cost. Furthermore, the
photoelectron emission material 61•6 may be any material as long as
it has a capability of emitting photoelectrons and for example, Au or the
like is preferable.

[0598]The photoelectron described above has energy different from that of
the primary electron beam, i.e. energy lower than that of the primary
electron beam. Here, the low energy refers to the order of several
electron volts to several tens of electron volts, preferably 0 to 10 eV.
The present invention can use any means for generating electrons of such
low energy. For example, a low energy electron gun (not shown) may be
provided in place of the UV lamp 61•5.

[0599]Further, in the case where energy of the electron gun is controlled,
the defect inspection apparatus of this embodiment comprises a power
supply 61•7. The negative pole of this power supply 61•7 is
connected to the photoelectron emission material 61•6, and the
positive pole is connected to the stage 61•2. Thus, the
photoelectron emission material 61•6 has a negative voltage applied
thereto with respect to the voltage of the stage 61•2 and the wafer
W. Energy of the low energy electron beam can be controlled with the
predetermined voltage.

[0600]The detector 61•3 may have any configuration as long as the
secondary electron image formed by the electrostatic lens 59•13 can
be converted into a signal capable of being subjected to post-processing.
For example, as shown in FIG. 62 in detail, the detector 61•3 may
comprise a micro-channel plate (MCP) 62•1, a fluorescent screen
62•2, a relay optical system 62•3, and an imaging sensor
62•4 constituted by a large number of CCD elements. The
micro-channel plate 62•1 has a large number of channels in a plate,
and further generates a large number of electrons while secondary
electrons or reflection electrons made to form an image by the
electrostatic lens 59•13 pass through the channels. That is, it
amplified secondary electrons. The fluorescent screen 62•2 converts
secondary electrons into light by emitting fluorescence by amplified
secondary electrons. The relay lens 62•3 guides the fluorescence to
the CCD imaging sensor 62•4, and the CCD imaging sensor 62•4
converts the intensity distribution of secondary electrons on the surface
of the wafer W into an electric signal or digital image data for each
element and outputs the same to the control unit 61•4.

[0601]The control unit 61•4 may be constituted by a general personal
computer 61•8. The computer 61•8 comprises a control unit
main body 61•9 performing various kinds of control and computation
processing according to a predetermined program, a CRT 61•10
displaying the result of processing by the main body, and an input unit
61•11 such as a keyboard and a mouse for an operator to input
commands. Of course, the control unit 61•4 may be constituted by
hardware dedicated to defect inspection apparatus, a workstation or the
like.

[0602]The control unit main body 61•9 is comprised of a CPU, a RAM,
a ROM, a hard disk and various kinds of control boards such as a video
board (not shown). A secondary electron image storage area for storing
electric signals received from the detector 61•3, i.e. digital
image data of secondary electron images of the wafer W is assigned on a
memory of a RAM, hard disk or the like. Furthermore, a defect detection
program 61•13 for reading secondary electron image data from a
storage area 61•12, and automatically detecting defects of the
wafer W according to a predetermined algorithm based on the image data is
stored on the hard disk in addition to a control program for controlling
the entire defect inspection apparatus. For example, the defect
inspection program 61•13 has a function to compare the inspection
site of the wafer W to another inspection site, and report a pattern
different from patterns of most other sites to the operator as defects
and display the pattern, for example. Further, a secondary electron image
61•14 may be displayed on a display unit of the CRT 61•10 to
detect defects of the wafer W by visual observation of the operator.

[0603]The action of the electron beam apparatus according to the
embodiment shown in FIG. 61 will now be described using the flowchart of
FIG. 63 as an example. First, the wafer W to be inspected is set on the
stage 61•2 (step 63•1). In this case, a large number of
wafers W stored in a loader (not shown) may be automatically set on the
stage 61•2 on a one-by-one basis. Then, a primary electron beam is
emitted from the electron gun 59•6, and applied to a predetermined
inspection area on the surface of the set wafer W through the
electrostatic lens 59•8 (step 63•2). Secondary electrons
and/or reflection electrons (hereinafter referred to only as "secondary
electrons") are emitted from the wafer W irradiated with the primary
electron beam and as a result, the wafer W is charged up to a positive
potential.

[0604]Then, a generated secondary electron beam is made to form an image
on the detector 61•3 under a predetermined magnification by the
electrostatic lens 59•13 in an enlarged projection system (step
S63•3). At this time, the UV lamp 61•5 is made to emit light
with a negative voltage applied to a photoelectron emission material
65•1 with respect to the stage 61•2 (step 63•4). As a
result, ultraviolet light with the frequency of ν emitted from the UV
lamp 61•5 causes photoelectrons to be emitted from the
photoelectron emission material 65•1 with its energy quantum of
hν (h represents Planck constant). The photoelectrons e.sup.- are
applied from the negatively charged photoelectron emission material
61•6 to the wafer W positively charged up to electrically
neutralize the wafer W. In this way, the secondary electron beam is made
to form an image on the detector 61•3 without being substantially
influenced by the positive potential of the wafer W.

[0605]The image of the secondary electron beam (having alleviated image
faults) emitted from the wafer W electrically neutralized in this way is
detected by the detector 61•3, and converted into digital image
data, and the image data is outputted (step 63•5). Then, the
control unit 61•4 carries out processing for detection of defects
of the wafer W based on the detected image data according to the defect
detection program 61•13 (step 63•6). In this defect detection
processing, the control unit 61•4 extracts a defective portion by
comparing detection images of detected dies as described previously if
the wafer has a large number of the same dies. A reference secondary
electron image of the wafer having no defects, previously stored in the
memory, may be compared with an actually detected secondary electron
image to automatically detect a defective portion. At this time, the
detection image may be displayed on the CRT 61•10, and a portion
judged as a defective portion may marked, whereby the operator can
finally check and determine whether the wafer W actually has defects or
not. A specific example of this defect detection process will be further
described later.

[0606]If it is determined that the wafer W has defects as a result of the
defect detection processing of step 63•5 (positive determination in
step 63•7), the operator is warned of existence of defects (step
63•8). As a method of warning, for example, a message indicating
existence of defects may be displayed on the display unit of the CRT
61•10, and at the same time, an enlarged image 61•14 of a
pattern having defects may be displayed. The defective wafer may be
immediately taken from the sample chamber 61•1, and stored in a
storage site different from a site for wafers having no defects (step
63•9).

[0607]As a result of the defect detection processing in step 63•6,
whether any area to be inspected still exists or not is determined for
the wafer W as a current inspection object (step 63•10) if it is
determined that the wafer W has no defects (negative determination in
step 63•7). If an area to be inspected still exists (positive
determination in step 63•10), the stage 61•2 is driven to
move the wafer W so that other area to be inspected next is within the
area irradiated with the primary electron beam (step 63•11). Then,
processing returns to step 63•2, where the same processing is
repeated for the other inspection area.

[0608]If no area to be inspected exists (negative determination in step
63•10), or after the step of taking the wafer (step 63•9),
whether the wafer W as a current inspection object is the last wafer or
not, i.e. whether or not any that has not been inspected yet exists on a
loader (not shown) is determined (step 63•12). If the wafer in not
the last wafer (negative determination in step 63•12), the
inspected wafer is stored in a predetermined place, and instead a new
wafer that has not been inspected yet is set on the stage 61•2
(step 63•13). Then, processing returns to step 63•2, where
the same processing is repeated for the wafer. If the wafer is the last
wafer (positive determination in step 63•12), the inspected wafer
is stores in a predetermined storage place to complete all steps. The
identification numbers of cassettes, the identification numbers of
wafers, for example, the lot numbers are stored for management.

[0609]Irradiation of UV photoelectrons (step 63•4) can be carried
out in any timing and within any time period as long as the secondary
electron image can be detected (step 63•5) in a state in which
positive charge-up of the wafer is avoided, and image faults are reduced.
The UV lamp 61•5 may be lit all the time while processing of FIG.
63 is continued, but the UV lamp 61•5 may be lit and unlit
periodically with the time period defined for each wafer. In the latter
case, as timing of light emission, light emission may be started before
the secondary electron beam is made to form an image (step 63•3)
and before the primary electron beam is applied (step 63•2), other
than the timing shown in FIG. 63. Irradiation of UV photoelectrons is
preferably continued at least during detection of secondary electrons,
but the irradiation of UV photoelectrons may be stopped even before or
during detection of the secondary electron image if the wafer is
electrically neutralized sufficiently.

[0610]Specific examples of the defect detection process at step 63•6
are shown in FIGS. 64(a) to (c). First, in FIG. 64(a), an image
64•1 of a die detected first and an image 64•2 of another die
detected second are shown. If it is determined that an image of another
die detected third is identical or similar to the first image 64•1,
it is determined that an area 64•3 of the second die image
64•2 has defects, and thus the defective area can be detected.

[0611]An example of measurement of a line width of a pattern formed on the
wafer is shown in FIG. 64(b). Reference numeral 64•6 denotes an
intensity signal of actual secondary electrons when an actual pattern
64•4 on the wafer is scanned in a direction 64•5, and a width
64•8 of an area where this signal continuously exceeds a threshold
level 64•7 defined by correction in advance can be measured as the
line width of the pattern 64•4. If the line width measured in this
way is not within a predetermined range, it can be determined that the
pattern has defects.

[0612]An example of measurement of a potential contrast of a pattern
formed on the wafer is shown in FIG. 64(c). In the configuration shown in
FIG. 61, an axis-symmetric electrode 64•9 is provided above the
wafer W and for example, a potential of -10 V is given with respect to
the wafer potential of 0 V. A equipotential surface of -2 V at this time
has a shape denoted by reference numeral 64•10. Here, patterns
64•11 and 64•12 formed on the wafer have potentials of -4 V
and 0 V, respectively. In this case, secondary electrons emitted from the
pattern 64•11 have a upward velocity equivalent to kinetic energy
of 2 eV at the -2 V equipotential surface 64•10, and therefore the
secondary electrons jump over the potential barrier 64•10, escape
from the electrode 64•9 as shown in an orbit 64•13, and are
detected by the detector 61•3. On the other hand, secondary
electrons emitted from the pattern 64•12 cannot jump over the -2 V
potential barrier, and is returned back to the wafer surface as shown in
an orbit 64•14, and therefore the secondary electrons are not
detected. Thus, the detection image of the pattern 64•11 is bright,
while the detection image of the pattern 64•12 is dark. In this
way, the potential contrast is obtained. If the brightness of the
detection image and the potential are corrected in advance, the potential
of the pattern can be measured from the detection image. The defective
area of the pattern can be evaluated from the potential distribution.

[0613]Furthermore, if there is an area floating in the die, an electric
charge can be added by the precharge unit to charge the floating area and
establish electrical connection to produce a potential difference between
the area and a grounded area. Potential contrast data in this state can
be acquired and analyzed to identify the floating area. It can be used as
a defect identification process when killer defects and the like exist.
The potential contrast data may be converted into a potential contrast
image to compare the potential contrast image with a potential contrast
image of a pattern of another die, or compare the potential contrast
image with a potential contrast image acquired from design data of the
CAD or the like.

[0614]FIG. 65 shows the outlined configuration of a defect inspection
apparatus comprising a precharge unit according to another embodiment of
the present invention. Furthermore, components the same as those of the
embodiment of FIG. 61 are given like symbols, and detailed descriptions
thereof are not presented. In this embodiment, as shown in FIG. 65, the
glass surface of the UV lamp 61•5 is not coated with the
photoelectron emission material. Instead, a photoelectron emission plate
65•1 is placed above the wafer W in the sample chamber 61•1,
and the UV lamp 61•5 is placed at a position such that emitted
ultraviolet light is applied to the photoelectron emission plate
65•1. The negative pole of a power supply 71•7 is connected
to the photoelectron emission plate 65•1, and the positive pole of
the power supply is connected to the stage 61•2. The photoelectron
emission plate 65•1 is made of metal such as Au, or may be a plate
coated with such a metal.

[0615]The action of the embodiment of FIG. 65 is the same as that of the
embodiment of FIG. 61. In the embodiment of FIG. 65, photoelectrons can
be applied to the surface of the wafer W as appropriate, and thus an
effect the same as that of the embodiment of FIG. 61 is exhibited.

[0616]FIG. 66 shows the outlined configuration of a defect inspection
apparatus comprising a precharge unit according to still another
embodiment of the present invention. Furthermore, components identical to
those of the embodiments of FIGS. 61 and 65 are given like symbols, and
detailed descriptions thereof are not presented. In the embodiment of
FIG. 66, as shown in this figure, a transparent window material
66•1 is provided on the side wall of the sample chamber 61•1,
and the UV lamp 61•5 is placed outside the sample chamber
61•2 so that ultraviolet light emitted from the UV lamp 61•5
is applied through the window material 66•1 to the photoelectron
emission plate 65•1 placed above the wafer W in the sample chamber
61•1. In the embodiment of FIG. 66, the UV lamp 61•5 is
placed outside the sample chamber 61•1 to be evacuated, and
therefore necessity to consider an anti-vacuum performance of the UV lamp
61•5 is eliminated, thus making it possible to widen a choice of
options of the UV lamp 61•5 compared to the embodiments of FIGS. 61
and 65.

[0617]Other actions of the embodiment of FIG. 66 are the same as those of
the embodiments of FIGS. 61 and 65. In the embodiment of FIG. 66,
photoelectrons can be applied to the surface of the wafer W as
appropriate, and therefore an effect the same as those of the embodiments
of FIGS. 61 and 65 is exhibited.

[0618]The embodiments have been described above, but the defect inspection
apparatus comprising the precharge unit according to the present
invention is not limited to the examples described above, but may be
changed as appropriate within the spirit of the present invention. For
example, the semiconductor wafer W is used as a sample to be inspected,
but the sample to be inspected of the present invention is not limited
thereto, and any type allowing defects to be detected with an electron
beam can be selected. For example, a mask having a pattern for exposure
of the wafer to light, a transparent mask (stencil mask) or the like may
be dealt with as an inspection object. Furthermore, the apparatus may be
used not only for the semiconductor process but also for inspection and
evaluation related to micro-machines and liquid crystals as a matter of
course.

[0619]Furthermore, as the electron beam apparatus for inspection of
defects, the configuration of FIGS. 61 to 66 is shown, but the
electro-optical system and the like may changed as appropriate. For
example, the electron beam irradiating means (59.6 and 59•8) of the
defect inspection apparatus shown in the figure makes the primary
electron beam enter the surface of the wafer W aslant from the above, but
means for deflecting the primary electron beam may be provided below the
electrostatic lens 59•13 to make the primary electron beam enter
the surface of the wafer W at a right angle. Such deflecting means
includes, for example, a Wien filter deflecting the primary electron beam
with a field E×B in which the electric field is orthogonal to the
magnetic field.

[0620]Further, as means for emitting photoelectrons, any means may be
employed as a matter of course other than the combination of the UV lamp
61•5 and the photoelectron emission member 61•6 or
photoelectron emission plate 65•1 shown in FIGS. 61 to 66.

[0621]The flow of the flowchart of FIG. 63 is not limited thereto. For
example, for a sample judged as being defective at step 63•7,
inspection of defects for other areas is not carried out, but the flow of
the process may be changed so that detection of defects is carried out
over all the areas. Furthermore, if the area to be irradiated with the
primary electron beam is enlarged so that one irradiation can cover all
the inspection area of the sample, steps 63•10 and 6:11 may be
omitted.

[0622]Further, in FIG. 63, if it is determined that the wafer has defects
at step 63•7, the operator is immediately warned of existence of
defects at step 63•8 and post-processing is carried out (step
63•9), but the flow may be changed so that defect information is
recorded, and after batch processing is completed (after positive
determination in step 63•12), defect information of the defective
wafer is reported.

[0623]As described in detail above, according to the defect inspection
apparatus and the defect inspection process according to the embodiments
of FIGS. 61 and 66, electrons having energy different from that of the
primary electron beam, i.e. energy lower than that of the primary
electron beam is supplied to the sample, and therefore an excellent
effect is obtained such that the positive charge-up on the sample surface
associated with emission of secondary electrons is reduced, and hence
image faults of the secondary electron beam associated with the charge-up
can be eliminated, thus making it possible to inspect defects of the
sample with high accuracy.

[0624]Further, if the defect inspection apparatus of FIGS. 61 and 66 is
used for the device production process, an excellent effect is obtained
such that the yield of products can be improved and defective products
can be prevented from being dispatched, because defect inspection for the
sample is carried out using the defect inspection apparatus described
above.

[0625]The case has been described above where the electron beam is softly
applied to the sample surface in low energy such that electron energy for
precharge is mainly 100 eV or less, but an image may be acquired in the
positive charge or negative charge mode or the reflection electron mode
after performing precharge at 2 kV to 20 kV, preferably 3 to 10 kV, more
preferably 3 to 5 kV. In the negative charge mode, precharge may be
performed in energy the same as landing energy of the electron beam
during inspection.

[0626]Furthermore, it is effective to coat the sample surface with a
conductive thin film for control of charge. The suitable thickness in
this case is 1 to 100 nm, preferably 1 to 10 nm, more preferably 1 to 3
nm. Further, if the image is acquired after the sample surface is cleaned
by sputter etching or the like, a cleaner image is obtained. Coating of
the conductive thin film and sputter etching may be used alone, or in
combination with precharge. For example, precharge may be performed to
acquire an image after sputter etching, or precharge may be performed
after coating of the conductive thin film after sputter etching.

2-5) Vacuum Pumping System

[0627]A vacuum pumping system is comprised of a vacuum pump, a vacuum
valve, a vacuum gage, vacuum piping and the like and an electro-optical
system, a detection unit, a sample chamber and a load lock chamber are
evacuated according to a predetermined sequence. In each unit, the vacuum
valve is controlled so as to achieve a required degree of vacuum. The
degree of vacuum is monitored all the time, and if an abnormality occurs,
emergency control of an isolation valve and the like is performed with an
interlock feature to ensure the degree of vacuum. For the vacuum pump, a
turbo-molecular pump is used for main pumping and a roots-type dry pump
is used for rough pumping. The practical pressure of the inspection site
(electron beam irradiation area) is 10-3 to 10-5 Pa, preferably
10-4 to 10-6 Pa lower by one order.

2-6) Control System

[0628]A control system is mainly comprised of a main controller, a
controlling controller and a stage controller. The main controller is
provided with a man-machine interface, through which the operation by the
operator is carried out (various kinds of instructions/command, input of
recipes and the like, instruction to start inspection, switching between
the automatic mode and the manual mode, input of all required commands
during the manual inspection mode, and the like). In addition,
communication with a host computer at a factory, control of the vacuum
pumping system, transportation of a sample such as a wafer, control of
alignment, transmission of commands to the other controlling controller
and stage controller, reception of information and the like are carried
out through the main controller. Furthermore, the controller comprises a
function to acquire image signals from an optical microscope, a stage
vibration correction function to make the electro-optical system feedback
a stage variation signal to correct deterioration of the image, and an
automatic focus correction function to detect a displacement of the
sample observation position in the Z direction (axial direction of the
secondary optical system), feedback the displacement to the
electro-optical system, and automatically correct the focus. Exchange of
feedback signals and the like with the electro-optical system, and
exchange of signals from the stage are performed through the controlling
controller and the stage controller, respectively.

[0629]The controlling controller is engaged in mainly control of an
electron beam optical system (control of electron gun, lens, aligner,
high accuracy power supply for Wien filter and the like). Specifically,
control is performed so that a constant electron current is always
applied to the irradiation area even when the magnification is changed,
and control for automatic voltage setting for each lens system and the
aligner matching each operation mode, and the like (interlock control),
such as automatic voltage setting for each lens system and the aligner
matching each magnification, is performed.

[0630]The stage controller mainly performs control relating to movement of
the stage to allow precise movement in X and Y directions in the order of
μm (with errors within about ±5 μm or smaller, preferably ±1
μm or smaller, more preferably ±0.5 μm or smaller). Furthermore,
in this stage, control in the rotational direction (θ control) is
performed with errors within about ±10 seconds, preferably ±1
second, more preferably ±0.3 seconds). The configuration of the
control system will be specifically described below.

2-6-1) Configuration and Function

[0631]This apparatus provides a function to image a specified position in
a wafer with an electron microscope or optical microscope and display the
same, a function to image the specified position in the wafer with the
electron microscope to detect and classify defects, and a function to
image the position at which defects are detected with the electron
microscope or optical microscope and display the same. Furthermore, for
achievement and maintenance of the above functions, the apparatus has an
electro-optical system control function, a vacuum system control
function, a wafer transportation control function, a single component
operation function, an imaging function, an automatic defect inspection
processing function, an apparatus abnormality detection function, and an
apparatus start/stop processing function.

(4) Single component operation function(5) Imaging functionA selection is
made from the following two input lines and an image is formed.

[0646](a) CCD camera

[0647]Optical microscope low power (pixel size: 2.75 μm/pix)

[0648]Optical microscope high power (pixel size: 0.25 μm/pix)

[0649](b) TDI camera

[0650](b-1) TDI-still

[0651](b-2) TDI-scan

[0652]EB×80 (pixel size: 0.2 μm/pix)

[0653]EB×160 (pixel size: 0.1 μm/pix)

[0654]EB×320 (pixel size: 0.05 μm/pix)

[0655]EB×480 (pixel size: 0.03 μm/pix).

[0656]Further, a user mode designation function is provided as a function
to limit operational items according to the skill/knowledge level of the
operator for prevention of an accident resulting from an erroneous
operation. This user mode is designated as a user ID and a password
inputted when a GUI (graphical user interface) is started.

[0657]The user mode includes a maintenance mode, a recipe creation mode,
and an operator mode, the operation is carried out in the maintenance
mode during setup work after installation of the apparatus and
maintenance work, necessary operations and procedures are supported in
the recipe creation mode during creation of a recipe, and inspection is
performed using the created recipe in the operator mode during automatic
defect inspection. The relation between each user mode and the apparatus
operation form is shown in FIG. 67.

[0661]This apparatus has an apparatus constant and a recipe as variable
parameters required for the operation. The apparatus constant is
specified as a parameter for absorbing apparatus specific errors (such as
a mounting error), and the recipe is specified as a parameter for
specifying various kinds of conditions to automatically perform defect
inspection. The apparatus constant is set during setup work and after
maintenance work, and is essentially unchanged thereafter.

[0662]The recipe is classified into a transportation recipe, an alignment
recipe, a die map recipe, a focus map recipe and an inspection recipe,
defect inspection is performed according to these recipes, setting work
is therefore carried out before inspection processing is performed, and a
plurality of patterns of settings are stored.

[0663]For the procedure during recipe creation, the wafer is conveyed onto
the stage (wafer is loaded) as a first step as shown in FIG. 68. After a
wafer cassette is installed in the apparatus, wafer search is carried out
to detect existence/nonexistence of the wafer in each slot in the
cassette, a wafer size, a notch/ori-fla type, and a notch direction (when
loaded onto the stage) are designated for the detected wafer, and the
wafer is loaded according to the procedure shown in FIGS. 69 and 70.
These conditions are stored in the transportation recipe. The direction
of placement of the die of the wafer loaded onto the stage does not
necessarily match the scan direction of the TDI camera (FIG. 71). In
order that the directions match each other, an operation for rotating the
wafer on a θ stage is required, and this operation is called
alignment (FIG. 72). Alignment practice conditions after the wafer is
loaded onto the stage are stored in the alignment recipe.

[0664]Furthermore, a die map (FIG. 73) showing the arrangement of dies
during alignment is created, the die size, the position of the origin die
(starting point showing the position of the die) and the like are stored
in the die map recipe.

2-6-2) Alignment Procedure

[0665]For the alignment (positioning) procedure, rough positioning is
performed with a low power of an optical microscope, then positioning is
performed with a high power of the optical microscope, and finally fine
positioning is performed with an EB image.

A. Imaging with Optical Microscope Low Power

(1) <First, Second and Third Search Die Designation and Template
Designation>

[0666](1-1) First Search Die Designation and Template Designation

[0667]The stage is moved by a user operation so that the lower left corner
of the die positioned below the wafer is positioned near the center of a
camera, the position is determined, and then a template image for pattern
matching is acquired. This die is a die serving as a reference for
positioning, and the coordinates of the lower left corner are coordinates
of a feature point. Hereinafter, pattern matching is performed with this
template image, whereby correct positional coordinates of any die on the
substrate are measured. For this template image, an image forming a
unique pattern in the search area must be selected.

[0668]Furthermore, in this example, the lower left corner is a template
image acquirement position for pattern matching, but the position is not
limited thereto, and any position in the die may be selected as a feature
point. Generally, however, since coordinates can be identified more
easily for the corners than for points in the die and on the edge of the
die, any one of the four corners is preferably selected. Similarly, in
this example, the template image for pattern matching is acquired for the
die positioned below the wafer but as a matter of course, any die may be
selected such that alignment can more easily be performed.

[0669](1-2) Second Search Die Designation

[0670]The die at the immediate right of the search die is designated as a
second search die, the stage is moved by a user operation so that the
lower left corner of the second search die is positioned near the center
of the camera, the position is determined, and then the template image
acquired in the procedure (1-1) is used to automatically perform pattern
matching, whereby accurate coordinate values of the second search die
matching the template image designated with the first search die is
acquired.

[0671]Furthermore, in this example, the die at the immediate right of the
first search die is the second search die, but the second search die of
the present invention is not limited thereto, as a matter of course. It
is essential that a point should be selected which makes it possible to
correctly know by pattern matching a positional relation of dies in the
line direction from the reference point with which the positional
coordinates of the correct feature point are known. Thus, for example,
the die at the immediate left of the first search die can be designated
as the second search die.

[0672](1-3) Third Search Die Designation

[0673]The die just above the second search die is designated as a third
die, the stage is moved by a user operation so that the lower left corner
of the third search die is positioned near the center of the camera, the
position is determined, and then the template image acquired in the
procedure (1-1) is used to automatically perform pattern matching,
whereby accurate coordinate values of the third search die matching the
template image designated with the first search die is acquired.

[0674]Furthermore, in this example, the die just above the second search
die is the third search die, but the third search die of the present
invention is not limited thereto, as a matter of course. It is essential
that a positional relation including distances of the coordinates of the
feature point of dies in the row direction can be known using, as a
reference, the die with which the correct coordinates of the feature
point are known. Thus, the die just above the first search die can be
suitably used as an alternate.

(2) <Optical Microscope Low Power Y Direction Pattern Matching>

[0675](2-1) The amount of movement to the pattern of the upper neighboring
die is calculated from the relation between the pattern match coordinates
(X2, Y2) of the second search die and the pattern match coordinates (X3,
Y3) of the third search die.

dX=X3-X2

dY=Y3-Y2

[0676](2-2) Using the calculated amount of movement (dX, dY), the stage is
moved to the coordinates (XN, YN) at which the pattern just above the
first search die exists (is expected to exist).

XN=X1+dX

YN=Y1+dY

[0677](X1, Y1): coordinates of pattern of first search die

[0678](2-3) After movement of the stage, imaging is performed with an
optical microscope low magnification, the template image is used to carry
out pattern matching to acquire the accurate coordinate values (XN, YN)
of the pattern that is currently observed, and 1 is set as an initial
value of a number of detected dies (DN).

[0679](2-4) The amount of movement (dX, dY) from the pattern coordinates
(X1, Y1) of the first search die to the coordinates (XN, YN) of the
pattern that is currently imaged is calculated.

dX=XN-X1

dY=YN-Y1

[0680](2-5) The stage is moved in an amount of movement (2*dX, 2*dY) twice
as large as the calculated amount of movement (dX, dY) with the first
search die as a starting point.

[0681](2-6) After movement of the stage, imaging is performed with an
optical microscope low magnification, the template image is used to carry
out pattern matching to update the accurate coordinate values (XN, YN) of
the pattern that is currently observed, and the number of detected dies
is increased by a factor of 2. See FIG. 74 for this procedure.

[0682](2-7) The procedures (2-4) to (2-6) are repeatedly carried out
toward the upper part of the wafer until a predesignated Y coordinate
value is exceeded.

[0683]Furthermore, in this example, to improve accuracy, to reduce the
number of processes (number of repetitions) and to reduce processing
time, movement is repeated in a twofold amount of movement. If there is
no problem with accuracy, and further reduction in processing time is
desired, movement may be carried out in a high integral multiple amount
greater than twofold amount, such as a three-fold or four-fold amount.
For further improvement in accuracy, movement may be repeated in a fixed
amount of movement. Any of these cases is incorporated in the number of
detected dies as a matter of course.

(3) <Optical Microscope Low Magnification 0 Rotation>

[0684](3-1) Using the amount of movement from the pattern coordinates (X1,
Y1) of the first search die to the accurate coordinate values (XN, YN) of
the pattern of the die searched lastly, and the number of dies (DN)
detected in the meantime, an amount of rotation (θ) and a die size
in the Y direction (YD) are calculated (see FIG. 75).

dX=XN-X1

dY=YN-Y1

θ=tan-1(dX/dY)

YD=sqrt((dX)2+(dY)2)/DN

*sqrt(A)=(A)1/2

[0685](3-2) The stage is rotated to θ in the calculated amount of
rotation (θ).

B. Imaging with Optical Microscope High Magnification(1) A procedure the
same as the procedure (1) for the optical microscope low magnification is
carried out using an optical microscope high magnification image.(2) A
procedure the same as the procedure (2) for the optical microscope low
magnification is carried out using an optical microscope high
magnification image.(3) A procedure the same as the procedure for the
optical microscope low magnification is carried out.(4) <Check of
Allowable Value after Optical Microscope High Power θ Rotation>

[0687]The coordinates (X'1, Y'1) of the first search die after rotation
are calculated from the coordinated (X1, Y1) before rotation and the
amount of rotation (θ), the stage is moved to the coordinates (X'1,
Y'1), the position is determined, and then a template image for pattern
matching is acquired.

[0689]The stage is moved in the Y direction by dY from the coordinates
(X'1, Y'1) of the first search die after rotation, and pattern matching
is carried out to acquire the accurate coordinate values (XN, YN) of the
pattern that is currently observed.

[0690](4-3) An amount of movement (dX, dY) from the coordinates (X'1, Y'1)
of the first search die after rotation to the coordinates (XN, YN) of the
pattern that is currently imaged is calculated.

dX=XN-X'1

dY=YN-Y'1

[0691](4-4) The stage is moved in an amount of movement (2*dX, 2*dY) twice
as large as the calculated amount of movement (dX, dY) with the first
search die as a starting point.

[0692](4-5) After movement of the stage, imaging is performed with an
optical microscope high magnification, and the template image is used to
carry out pattern matching to update the accurate coordinate values (XN,
YN) of the pattern that is currently observed.

[0693](4-6) The procedures (4-3) to (4-5) are repeatedly carried out
toward the upper part of the wafer until a predesignated Y coordinate
value is exceeded.

[0694](4-7) Calculation of rotation of θ

[0695]Using the amount of movement from the coordinates (X'1, Y'1) of the
first search die after rotation to the accurate coordinate values (XN,
YN) of the pattern of the die searched lastly, an amount of rotation
(θ) is calculated.

[0697]Whether the amount of rotation (θ) calculated in the procedure
(4-7) equals a predefined value or smaller is checked. If the amount of
rotation (θ) is greater than the predefined value, the calculated
amount of rotation (θ) is used to rotate the stage to θ, and
then the procedures (4-1) to (4-8) are carried out again. However, in
case where the amount of rotation (θ) is not within an allowable
range even if the procedures (4-1) to (4-8) are carried out a specified
number of times, the operation is considered as an error and processing
is stopped.

C. Alignment with EB Image

(1) <Y Search First Die, Designation of Template of EB>

[0698]A procedure the same as the procedure (1) for the optical microscope
high magnification is carried out using an EB image.

(2) <EB: Y Direction Pattern Matching>

[0699]A procedure the same as the procedure (2) for the optical microscope
high magnification is carried out using an EB image.

(3) <EB: θ Rotation>

[0700]A procedure the same as the procedure (3) for the optical microscope
high magnification is carried out using an EB image.

(4) <EB: check of allowable value after θ Rotation>

[0701]A procedure the same as the procedure (4) for the optical microscope
high magnification is carried out using an EB image.

(5) The procedures (1) to (4) are carried out using an EB image of a high
magnification as required.(6) An appropriate value of an X direction die
size (XD) is calculated from the coordinates (X1, Y1) of the first search
die and the coordinates (X2, Y2) of the second search die.

dX=X2-X1

dY=Y2-Y1

XD=sqrt((dX)2+(dY)2)

sqrt(A)= A

D. Creation of Die Map Recipe

[0702](1) <X search first die, designation of template of EB>

[0703]The stage is moved by a user operation so that the lower left corner
of the die positioned at the left end of the wafer is positioned near the
center of a TDI camera, the position is determined, and then a template
image for pattern matching is acquired. For this template image, an image
forming a unique pattern in the search area must be selected.

(2) <EB: X Direction Pattern Matching>

[0704](2-1) The approximate value of the X direction die size (XD) is used
to move the stage to coordinates (X1+XD, Y1) at which the pattern of the
die at the immediate right of the X search first die exists (is expected
to exist).

[0705](2-2) After movement of the stage, an EB image is formed by the TDI
camera, the template image is used to perform pattern matching to acquire
the accurate coordinates (XN, YN) of the pattern that is currently
observed, and 1 is set as an initial value of the number of detected dies
(DN).

[0706](2-3) An amount of movement (dX, dY) from the pattern coordinates of
the X search first die to the coordinates (XN, YN) of the pattern that is
currently observed.

dX=XN-X1

dY=YN-Y1

[0707](2-4) The stage is moved in an amount of movement (2*dX, 2*dY) twice
as large as the calculated amount of movement (dX, dY) with the X search
first die as a starting point.

[0708](2-5) After movement of the stage, an EB image is formed by the TDI
camera, the template image is used to perform pattern matching to update
the accurate coordinates (XN, YN) of the pattern that is currently
observed, and the number of detected dies is increased by a factor of 2.

[0709](2-6) The procedures (2-3) to (2-5) are repeatedly carried out in
the right direction of the wafer until a predesignated X coordinate value
is exceeded.

(3) <Calculation of X Direction Gradient>

[0710]A stage movement direct error (Φ) and an X direction die size
(XD) are calculated using the amount of movement from the pattern
coordinates (X1, Y1) of the X search first die to the accurate coordinate
values (XN, YN) of the pattern of the die searched lastly, and the number
of dies (DN) detected in the meantime.

dX=XN-X1

dY=YN-Y1

Φ=tan-1(dX/dY)

XD=sqrt((dX)2+(dY)2)/DN

sqrt(A)= A

(4) <Creation of Die Map>

[0711]In this way, the X direction die size (XD) is determined, and it is
combined with the Y direction die size (YD) previously determined when
the amount of rotation (θ) is calculated to create a die map
(information of an ideal arrangement of dies). From the die map, an ideal
arrangement of dies is known. On the other hand, actual dies on the
substrate are influenced by, for example, mechanical errors of the stage
(errors of parts such as a guide, and assembly), errors of an
interferometer (e.g. due to problems of assembly of a mirror or the
like), and deformation of the image due to charge-up, and may not be
necessarily observed as an ideal arrangement, but the error between the
position of the actual dies and the ideal arrangement on the die map is
known, and this error is considered and automatically corrected while
inspection is carried out.

E. Procedure for Creation of Focus Recipe

[0712]A procedure for creation of a focus recipe will now be described.
The focus recipe stores information of an optimum focus position at any
position on the surface of a sample such as a substrate, or various
conditions about the focus position in a predetermined format such as a
table. In a focus map recipe, focus conditions are set only for
designated positions on the wafer, and focus values between designated
positions are linearly interpolated (see FIG. 76). The procedure for
creation of a focus recipe is as follows.

[0715](3) The stage is moved to each measurement point, and a focus value
(CL12 voltage) is manually adjusted based on an image and a contrast
value.

[0716]The die map created by alignment processing provides ideal position
information calculated from die coordinates at the both ends of the
wafer, and an error occurs between the die position on the die map and
the actual die position due to various factors (see FIG. 77). A procedure
for creating parameters for absorbing the error is called fine alignment,
and information of the error between the die map (ideal die position
information) and the actual die position is stored in a fine alignment
recipe. The information set here is used during defect inspection. In the
fine alignment recipe, errors are measured only for dies designated on
the die map, and errors between designated dies are lineally
interpolated.

F. Fine Alignment Procedure

[0717](1) Error measurement object dies for fine alignment are designated
from the die map.(2) A reference die is selected from the error
measurement object dies, and the position of the reference die is defined
as a point where the error with the die map is zero.

[0718](3) The lower left corner of the reference die is imaged by the TDI
camera to acquire a template image for pattern matching.

*A unique pattern in the search area is selected as a template image.(4)
Coordinates (X0, Y0) (on the die map) at the lower left of the
neighboring error measurement object die is acquired, and the stage is
moved. After movement of the stage, imaging is performed by the TDI
camera, and pattern matching is carried out using the template image of
the procedure (3) to acquire accurate coordinate values (X, Y).(5) Error
between the coordinate values (X, Y) acquired by pattern matching and
coordinate values (X0, Y0) on the die map are stored.(6) The procedures
(4) and (5) are carried out for all the error measurement object dies.

2-6-3) Defect Inspection

[0719]For defect inspection, as shown in FIG. 78, conditions of the
electro-optical system are set (imaging magnification and the like are
set), the stage is moved while irradiating an electron beam to perform
TDI scan imaging (FIG. 79), and defect inspection is carried out in real
time by an inspection dedicated processing unit (IPE) according to the
set inspection conditions (array inspection conditions, random inspection
conditions, inspection areas).

[0720]In an inspection recipe, conditions of the electro-optical system,
inspection object dies, inspection areas, the inspection process
(random/array) and the like are set (A and B of FIG. 80).

[0721]Furthermore, to acquire stable images for defect inspection, EO
correction for inhibiting blurring of formed images resulting from
positional deviations and speed unevenness, die position correction for
absorbing errors between the ideal arrangement on the die map and the
actual die position, and focus adjustment for interpolating focus values
of the entire wafer area using focus values previously measured at finite
measurement points are simultaneously carried out in real time.

[0722]In the scan operation of defect inspection, the entire area of the
inspection object die is inspected (FIG. 81) and in addition, as shown in
FIG. 82, the amount of step movement in a direction perpendicular to the
scan direction is adjusted, whereby thinned-out inspection can be
performed (reduction in inspection time).

[0723]After inspection, the number of defects, positions of dies including
defects, defect sizes, defect positions in dies, defect types, defective
images and reference images are displayed on a display as inspection
results, and information thereof, recipe information and the like are
stored in a file, whereby results of inspection in the past can be
confirmed and reproduced.

[0724]During automatic defect inspection, various kinds of recipes are
selected and designated, whereby the wafer is loaded according to the
transportation recipe, alignment of the wafer is performed on the stage
according to the alignment recipe, focus conditions are set according to
the focus map recipe, inspection is carried out according to the
inspection recipe, and the wafer is unloaded according to the
transportation recipe (A and B of FIG. 83).

2-6-4) Control System Configuration

[0725]This apparatus is comprised of a plurality of controllers as shown
in FIG. 84. A main controller conducts GUI unit/sequence operations of
the apparatus (EBI), receives operation commands from a factory host
computer or GUI, and gives necessary instructions to a VME controller and
an IPE controller. The VME controller conducts operations of components
of the apparatus (EBI), and gives instructions to a stage controller and
a PLC controller according to the instructions from the main controller.
The IPE controller acquires defect inspection information from an IPE
node computer, classifies the acquired defects and displays an image
according to the instructions from the main controller. The IPE node
computer acquires an image outputted from the TDI camera and carries out
defect inspection.

[0726]Upon reception of the instructions from the VME controller, the PLC
controller drives devices such as valves, acquires sensor information,
and monitors abnormalities such as a vacuum abnormality that should be
monitored all the time. Upon reception of the instructions from the VME
controller, the stage controller conducts movement in the XY direction
and rotation of the wafer placed on the stage.

[0727]By forming such a distributed control system, interfaces between the
controllers are kept the same to eliminate the necessity to change
software and hardware of the upper-level controller if an apparatus
component at the end is changed. Furthermore, even if a sequence
operation is added/modified, a change in upper-level software and
hardware is minimized, whereby a change in configuration can be flexibly
coped with.

2-6-5) User Interface Configuration

[0728]FIG. 85 shows the device configuration of a user interface.

(1) Input Unit

[0729]The input unit is a device receiving inputs from the user, and is
comprised of a "keyboard", a "mouse" and a "JOY pad".

(2) Display Unit

[0730]The display unit is a device displaying information to the user, and
is comprised of two monitors.

[0731]In this apparatus, the following three coordinate systems are
specified.

(1) Stage Coordinate System [XS, YS]

[0732]This is a reference coordinate system for indicating a position
during control of a stage position.

[0733]The X coordinate value is incremented in the rightward direction and
the Y coordinate value is incremented in the upward direction with the
lower left corner of a chamber as an origin.

[0734]This apparatus has only one coordinate system as this coordinate
system.

[0735]The position (coordinate values) shown in the stage coordinate
system is situated at the center of the stage (center of the wafer).

[0736]That is, if the coordinate values [0,0] are designated in the stage
coordinate system, the stage is moved so that the center of the stage
(center of the wafer) is superimposed on the origin of the stage
coordinate system.

[0737][μm] is used as a unit, but the minimum resolution is
λ/1024 (≈0.618 [nm]).

[0738]*λ: wavelength of a laser for use in the laser interferometer
(λ≈632.99 [nm]).

(2) Wafer Coordinate System [XW, YW]

[0739]The coordinates are reference coordinates for indicating a position
of observation (imaging/display) on the wafer.

[0740]The X coordinate value is incremented in the rightward direction and
the Y coordinate value is incremented in the upward direction with the
center of the wafer as an origin.

[0741]The position (coordinate values) shown in the wafer coordinate
system is situated at the center of imaging by an imaging device (CCD
camera, TDI camera) selected at this time.

[0742]This apparatus has only one coordinate system as this coordinate
system.

[0743][μm] is used as a unit, but the minimum resolution is
λ/1024 (≈0.618 [nm]).

[0744]*λ: wavelength of a laser for use in the laser interferometer
(λ≈632.99 [nm]).

(3) Die coordinate system [XD, YD]

[0745]The coordinates are reference coordinates for specifying a position
of observation (imaging/display) in each die.

[0746]The X coordinate value is incremented in the rightward direction and
the Y coordinate value is incremented in the upward direction with the
lower left corner of each die as an origin. This coordinate system exists
in each die. [μm] is used as a unit, but the minimum resolution is
λ/1024 (≈0.618 [nm]).

[0747]*λ: wavelength of a laser for use in the laser interferometer
(λ≈632.991 [nm]).

[0748]Furthermore, dies on the wafer are numbered (subjected to
numbering), and a die serving as a reference for numbering is called an
origin die. By default, the die closest to the origin of the wafer
coordinate system is the origin die, but the position of the origin die
can be selected according to designation by the user.

[0749]The relation between the coordinate values in each coordinate system
and the position of observation (display) is shown in FIG. 86. * The
relation between coordinates indicated by a user interface and the
direction of movement of the stage is as follows.

(1) Joystick & GUI arrow button

[0750]The direction indicated by a joystick and a GUI arrow button is
considered as a direction in which the operator wants to make an
observation, and the stage is moved in a direction opposite to the
indicated direction.

Example

[0751]Indicated direction: right . . . direction of movement of stage:
left (image shifts to the left=field of view shifts to the right).

[0753]The coordinates directly inputted on the GUI are considered as a
position in which the operator wants to make an observation on the wafer
coordinate system, and the stage is moved so that the wafer coordinates
are displayed at the center of the formed image.

2-7) Descriptions of Other Functions and Configurations

[0754]FIG. 87 shows the overall configuration of this embodiment. However,
part of the configuration is omitted. In this figure, an inspection
apparatus has a primary column 87•1, a secondary column 87•2
and a chamber 87•3. An electron gun 87•4 is provided in the
primary column 87•1, and a primary optical system 87•5 is
placed on the optical axis of an electron beam (primary beam) emitted
from the electron gun 87•4. Furthermore, a stage 87•6 is
placed in the chamber 87•3, and a sample W is placed on the stage
87•6.

[0755]An objective lens 87•7, a numerical aperture 87•8, a
Wien filter 87•9, a second lens 87•10, a field aperture
87•11, a third lens 87•12, a fourth lens 87•13 and a
detector 87•14 are placed on the optical axis of a secondary beam
emitted from the sample W in the secondary column 87•2.
Furthermore, the numerical aperture 87•12 corresponds to an
aperture diaphragm, and is a thin plate made of metal (Mo) having a
circular hole. The aperture is situated at the crossover position of the
primary beam and the back focal position of the objective lens
87•7. Thus, the objective lens 87•7 and the numerical
aperture 87•8 constitute a telecentric electro-optical system.

[0756]On the other hand, an output of the detector 87•14 is inputted
to a control unit 87•15, and an output of the control unit
87•15 is inputted to a CPU 87•16. A control signal of the CPU
87•16 is inputted to a primary column control unit 87•17, a
secondary column control unit 87•18 and a stage drive mechanism
87•19. The primary column control unit 87•17 controls a lens
voltage of the primary optical system 87•5, the secondary column
control unit 87•18 controls lens voltages of the objective lens
87•8 and the second to fourth lenses 87•10 to 87•13,
and controls an electromagnetic field applied to the Wien filter
87•9.

[0757]Furthermore, the stage drive mechanism 87•19 transmits
position information of the stage to the CPU 87•16. Further, the
primary column 87•1, the secondary column 87•2 and the
chamber 87•3 are connected to a vacuum pumping system (not shown),
and are evacuated by a turbo-molecular pump of the vacuum pumping system
to maintain vacuum conditions therein.

[0758](Primary beam) The primary beam from the electron gun 87•4
enters the Wien filter 87•9 while receiving a lens action by the
primary optical system 87•5. Here, as a tip of the electron gun,
LaB6 enabling a large current to be taken with a rectangular cathode
is used. Furthermore, for the primary optical system 72, a rotation
axis-asymmetric quadrupole or octpole electrostatic (or electromagnetic)
lens is used. This can cause convergence and divergence on the X and Y
axes, respectively, as in the case of so called a cylindrical lens. This
lens is formed in two, three or four stages, and conditions of each lens
are optimized, whereby the beam irradiation area on the sample surface
can be formed into any rectangular or elliptic shape without causing a
loss of irradiation electrons.

[0759]Specifically, if the electrostatic quadrupole lens is used, four
circular column rods are placed around the optical axis. Opposite
electrodes are potential-equalized, and given opposite voltage
characteristics in phases shifted at a right angle to each other around
the optical axis.

[0760]Furthermore, as the quadrupole lens, a lens having a shape such that
a circular plate usually used as an electrostatic deflector quadrisected
may be used instead of a circular column lens. In this case, the lens can
be downsized. The primary beam passing through the primary optical system
72 has its orbit bent by a deflection action of the Wien filter
87•9. The Wien filter 87•9 orthogonalizes the magnetic field
and the electric field, makes only charged particles satisfying the Wien
condition of E=vB travel in a straight line where E is the electric
field, B is the magnetic field, and v is the velocity of charged
particles, and bends the orbit of other charged particles. For the
primary beam, a force FB by the magnetic field and a force FE by the
electric force are produced, and thus the beam orbit is bent. On the
other hand, for the secondary beam, the force FB and the force FE act in
opposite directions, and are thus mutually canceled, and therefore the
secondary beam travels in a straight line.

[0761]The lens voltage of the primary optical system 87•5 is
previously set so that the primary beam is made to form an image at the
aperture of the numerical aperture 87•8. The numerical aperture
87•8 inhibits arrival at the sample surface of an excessive
electron bean scattered in the apparatus, thus preventing charge-up and
contamination of the sample W. Further, since the numerical aperture
87•8 and the objective lens 87•7 constitute a telecentric
electro-optical system, the primary beam passing through the objective
lens 87•7 is a parallel beam, and is equally and uniformly applied
to the sample W. That is, Koehler illumination is achieved as in the
optical microscope.

[0762](Secondary beam) When the primary beam is irradiated to the sample,
secondary electrons, reflection electrons or back-scattered electrons are
generated as secondary particles from the beam irradiation surface of the
sample.

[0763]The secondary particles passes through the lens while receiving a
lens action by the objective lens 87•7. The objective lens
87•7 is constituted by three electrodes. The lowermost electrode is
designed to form a positive electric field with a potential on the sample
W side to attract electrons (particularly secondary electrons having low
directivity) and guide the electrons into the lens efficiently.
Furthermore, the lens action is achieved by applying a voltage to first
and second electrodes of the objective lens 87•7, and keeping the
third electrode at zero potential. On the other hand, the numerical
aperture 87•8 is situated at the position of the focus of the
objective lens 87•7, i.e. the position of the back focal position
from the sample W. Thus, a light flux of the electron beam exiting from
an acentric (off-axis) area of the field of view passes through the
central position of the numerical aperture 87•8 as a parallel beam
without causing an eclipse.

[0764]Furthermore, the numerical aperture 87•8 plays a role to
reduce lens aberrations of the second to fourth lenses 87•10 to
87•13 for the secondary beam. The secondary beam passing through
the numerical aperture 87•8 travels away in a straight line without
receiving a deflection action of the Wien filter 87•9. Furthermore,
by changing the electromagnetic field applied to the Wien filter
87•9, only electrons having specific energy (e.g. secondary
electrons, or reflection electrons, or back-scattered electrons) can be
guided to the detector 87•14.

[0765]If secondary particles are made to form an image by the objective
lens 87•7 alone, the lens action becomes so strong that the
aberration tends to occur. Thus, the secondary particles are made to form
an image one time by a combination of the objective lens 87•7 and
the second lens 87•10. The secondary particles are subjected to
intermediate imaging on the field aperture 87•11 by the objective
lens 87•7 and the second lens 87•10. In this case, usually,
the magnification necessary as the secondary optical system is often
insufficient, and thus as a lens for magnifying the intermediate image,
the third lens 87•12 and the fourth lens 87•13 are added. The
secondary particles are made to form an image under magnification by the
third lens 87•12 and the fourth lens 87•13, respectively,
i.e. they are made to form an image total three times here. Furthermore,
they may be made to form an image one time (total twice) by the third
lens 87•12 and the fourth lens 87•13 in combination.

[0766]Furthermore, the second to fourth lenses 87•10 to 87•13
are each a rotation axis-symmetric lens called a unipotential or Einzwell
lens. Each lens is comprised of three electrodes, in which two outside
electrodes are usually at zero potential, and the lens is caused to
perform a lens action and controlled with a voltage applied to the
central electrode. Furthermore, the field aperture 87•11 is
situated at the intermediate imaging point. The field aperture
87•11 limits the field of view to a necessary range like a field
diaphragm of an optical microscope, but in the case of the electron beam,
an excessive beam is blocked with the third lens 87•12 and the
fourth lens 87•13 to prevent charge-up and contamination of the
detector 87•14. Furthermore, the magnification is set by changing
the lens conditions (focal distance) of the third lens 87•12 and
the fourth lens 87•13.

[0767]The secondary particles are projected under magnification by the
secondary optical system, and form an image on the detection surface of
the detector 87•14. The detector 87•14 is comprised of an MCP
amplifying electrons, a fluorescent screen converting electrons into
light, a lens for communicating between the vacuum system and the outside
and transmitting an optical image and other optical elements, and an
imaging device (CCD, etc.). The secondary particles form an image on the
MCP detection surface and amplified, and electrons are converted into
optical signals by the fluorescent screen, and converted into
photoelectric signals by the imaging element.

[0768]The control unit 87•15 reads an image signal of the sample
from the detector 87•14, and transmits the signal to the CPU
87•16. The CPU 87•16 carries out defect inspection of the
pattern by template matching or the like from the image signal.
Furthermore, the stage 87•6 can be moved in the XY direction by the
stage drive mechanism 87•19. The CPU 87•16 reads the position
of the stage 87•6, outputs a drive control signal to the stage
drive mechanism 87•19, drives the stage 87•6, and performs
detection and inspection of images one after another.

[0769]In this way, in the inspection apparatus of this embodiment, the
numerical aperture 87•8 and the objective lens 87•7
constitute a telecentric electro-optical system, thus making it possible
to uniformly irradiate the beam to the sample for the primary beam. That
is, Koehler illumination can easily be achieved.

[0770]Further, for secondary particles, all main beams from the sample W
enter the objective lens 87•7 at a right angle (in parallel to the
lens optical axis), and pass through the numerical aperture 87•8,
and therefore periphery light is not eclipsed, and the image brightness
of the periphery of the sample is not reduced. Furthermore, position of
image formation varies, i.e. a transverse chromatic aberration occurs due
to variations in energy of electrons (particularly, secondary electrons
have large variations in energy, and therefore cause a large transverse
chromatic aberration), but this transverse chromatic aberration can be
inhibited by placing the numerical aperture 87•8 at the focus point
of the objective lens 87•7.

[0771]Furthermore, since the magnification is changed after the beam
passes through the numerical aperture 87•8, a uniform image can be
obtained over the entire field of view at the detection side even if the
set powers of lens conditions of the third lens 87•10 and the
fourth lens 87•13 are changed. Furthermore, in this embodiment, a
uniform image having no unevenness can be acquired but usually, if the
magnification is increased, the problem arises such that the brightness
of the image is reduced. Thus, to solve this problem, the lens conditions
of the primary optical system are set so that when the lens conditions of
the secondary optical system are changed to change the magnification, the
effective field of view on the sample surface determined accordingly and
the electron beam irradiated to the sample surface have the same size.

[0772]That is, if the magnification is increased, the field of view is
reduced accordingly, but by increasing the current density of the
electron beam, the signal density of detection electrons is kept
constant, and thus the brightness of the image is not reduced, even if
the electron beam is projected under magnification by the secondary
optical system.

[0773]Furthermore, in the inspection apparatus of this embodiment, the
Wien filter 87•9 bending the orbit of the primary beam and making
the secondary beam travel in a straight line is used, but the Wien filter
is not limited to this configuration, and the apparatus may have a
configuration using a Wien filter making the orbit of the primary beam
travel in a straight line and bending the orbit of the secondary beam.
The E×B is used here, but only a magnetic field may be used. In
this case, for example, both the direction in which primary electrons
enter and direction in which signal electrons are made to travel toward
the detector may follow a Y-shaped configuration.

[0774]Furthermore, in this embodiment, a rectangular beam is formed from a
rectangular cathode and a quadrupole lens, but the invention is not
limited thereto and, for example, a rectangular or elliptic beam may be
made from a circular beam, or a circular beam may be made to pass through
a slit to take a rectangular beam. Furthermore, either a linear beam or a
plurality of beams may be used, and they may be scanned.

2-7-1) Control Electrode

[0775]An electrode approximately axisymmetric to an irradiation optical
axis of an electron beam (25•8 in FIG. 25-1) is placed between the
objective lens 87•7 and the wafer W. Examples of the shape of the
electrode are shown in FIGS. 88 and 89. FIGS. 88 and 89 are perspective
views of electrodes 88•1 and 89•1. FIG. 88 is a perspective
view showing the electrode 88•1 having an axisymmetrically
cylindrical shape, and FIG. 89 is a perspective view showing the
electrode 89•1 having an axisymmetrically discoid shape.

[0776]In this embodiment, the electrode 88•1 having a cylindrical
shape shown in FIG. 88 is used, but the electrode 89•1 having a
discoid shape shown in FIG. 89 may be used as long as it is approximately
axisymmetric to the irradiation optical axis of the electron beam.
Further, a predetermined voltage (negative potential) lower than a
voltage applied to the wafer W (potential is 0 V because the wafer W is
grounded in this embodiment) is applied to the electrode 88•1 by
the power supply 25•9 to generate an electric field for preventing
a discharge between the objective lens 87•7 (25•7 in FIG.
25-1) and the wafer W. A potential distribution between the wafer W and
the objective lens 97•7 at this time will be described with
reference to FIG. 90.

[0777]FIG. 90 is a graph showing a voltage distribution between the wafer
W and the objective lens 87•7. This figure shows a voltage
distribution from the wafer W to the position of the objective lens
87•7 with the position on the irradiation optical axis of the
electron beam as a horizontal axis. In the conventional electron beam
apparatus having no electrode 88•1, the voltage distribution from
the objective lens 87•7 to the wafer W gently changes up to the
grounded wafer W with the voltage applied the objective lens 87•7
being the maximum (narrow line in FIG. 90), while in the electron beam
apparatus of this embodiment, the electrode 88•1 is placed between
the objective lens 87•7 and the wafer W, and a predetermined
voltage (negative potential) lower than a voltage applied to the wafer is
applied to the electrode 88•1, so that the electric field of the
wafer W is weakened (thick line in FIG. 90). Accordingly, in the electron
beam apparatus of this embodiment, the electric field is not concentrated
near the via 25•13 in the wafer (FIG. 25-1), and thus the electric
field is not increased. If the electron beam is applied to the via
25•13 to emit secondary electrons, the emitted secondary electrons
are not accelerated to the extent that residual gas is ionized, thus
making it possible to prevent a discharge occurring between the objective
lens 87•7 and the wafer W.

[0778]Furthermore, since a discharge can be prevented between the
objective lens 87•7 and the via 25•13 (FIG. 25-1), there is
no possibility that the pattern of the wafer W and the like are damaged
with discharge. Furthermore, in the embodiment described above, a
discharge between the objective lens 87•7 and the wafer W having
the via 25•3 can be prevented, but since a negative potential is
applied to the electrode 88•1, the efficiency of detection of
secondary electrons by the detector 87•14 may be reduced.
Accordingly, if the detection efficiency is reduced, a series of
operations of irradiating the electron beam to detect secondary electrons
are carried out two or more times, and a plurality of obtained detection
results are subjected to processing such as cumulative addition and
equalization to obtain a predetermined signal quality (S/N ratio of
signal). This embodiment is described using a signal to noise ratio (S/N
ratio) as the detection efficiency as one example.

[0779]The secondary electron detection operation will now be described
with reference to FIG. 91. FIG. 91 is a flowchart showing the secondary
electron detection operation of the electron beam apparatus. First,
secondary electrons from an inspection subject sample are detected by the
detector 87•14 (step 91•1). Then, whether the signal to noise
ratio (S/N ratio) is equal to or greater than a predetermined value or
not is determined (step 91•2). If the signal to noise ratio is
equal to or greater than the predetermined value at step 91•2, it
means that secondary electrons have been detected sufficiently by the
detector 87•14, and thus the secondary electron detection operation
is ended.

[0780]On the other hand, if the signal to noise ratio is smaller than the
predetermined value at step 91•2, a series of operations of
irradiating the electron beam to detect secondary electrons are carried
out 4N times, and equalization processing is carried out (step
91•3). Here, since the initial value of N is set to "1", the
secondary electron detection operation is carried out 4 times at the
initial round at step 91•3.

[0781]Then, "1" is added to N to count up (step 91•4), and again
whether the signal to noise ratio is equal to or greater than the
predetermined value is determined at step 91•2. Here, if the signal
to noise ratio is smaller than the predetermined value, processing
proceeds to step 91•3 again, where the secondary electron detection
operation is carried out 8 times in this case. Then, N is counted up, and
steps 91•2 to 91•4 are repeated until the signal to noise
ratio is equal to or greater than the predetermined value.

[0782]Furthermore, in this embodiment, a predetermined voltage (negative
potential) lower than a voltage applied to the wafer W is applied to the
electrode 88•1 to prevent a discharge to the wafer W having the via
25•13 but in this case, the efficiency of detection of secondary
electrodes may be reduced. Accordingly, if the inspection subject sample
is a type of inspection subject sample hard to cause a discharge between
itself and the objective lens 87•7, such as a wafer having no via,
the voltage applied to the electrode 88•1 can be controlled so that
the efficiency of detection of secondary electrons in the detector
87•14 is improved.

[0783]Specifically, even when the inspection subject sample is grounded, a
predetermined voltage higher than the voltage applied to the inspection
subject sample, for example a voltage of +10 V is applied to the
electrode 88•1. Furthermore, at this time, the distance between the
electrode 88•1 and the inspection subject sample is set to a
distance such that no discharge occurs between the electrode 88•1
and the inspection subject sample.

[0784]In this case, secondary electrons generated by irradiation of the
electron beam to the inspection subject sample are accelerated toward the
detector 87•14 side by an electric field generated with the voltage
applied to the electrode 88•1. The secondary electrons are further
accelerated toward the detector 87•14 side with an electric field
generated with a voltage applied to the objective lens 87•7 and
subjected to a convergence action, and therefore a large number of
secondary electrons enter the detector 87•14, thus making it
possible to the detection efficiency.

[0785]Furthermore, the electrode 88•1 is axisymmetric, and thus has
a lens action for convergence of the electron beam applied to the
inspection subject sample. Thus, the primary electron beam can be more
finely focused with the voltage applied to the electrode 88•1.
Furthermore, since the primary electron beam can be finely focused with
the electrode 88•1, an objective lens system having a lower
aberration can be formed with a combination with the objective lens
87•7. The electrode 88•1 may be approximately axisymmetric to
the extent that this lens action can be achieved.

[0786]According to the electron beam apparatus of the embodiment described
above, an electrode having a shape approximately axisymmetric to the
irradiation axis of the electron beam and controlling the intensity of
the electric field on the surface of the inspection subject sample
irradiated with the electron beam is provided between the inspection
subject sample and the objective lens, thus making it possible to control
the electric field between the inspection subject sample and the
objective lens.

[0787]An electrode having a shape approximately axisymmetric to the
irradiation axis of the electron beam and reducing the intensity of the
electric field on the surface of the inspection subject sample irradiated
with the electron beam, thus making it possible to eliminate a discharge
between the inspection subject sample and the objective lens.
Furthermore, since alterations such as reduction of the voltage applied
to the objective lens are not made, secondary electrons can be made to
pass through the objective lens efficiently, thus making it possible to
improve the detection efficiency and obtain a signal having a good S/N
ratio.

[0788]The voltage for reducing the intensity of the electric field on the
surface of the inspection subject sample irradiated with the electron
beam can be controlled depending on the type of inspection subject
sample. For example, if the inspection subject sample is a type of
inspection subject sample that tends to cause a discharge between itself
and the objective lens, the discharge can be prevented by changing the
voltage of the electrode to reduce the intensity of the electric field on
the surface of the inspection subject sample irradiated with the electron
beam.

[0789]The voltage given to the electrode can be changed, i.e. the voltage
for reducing the intensity of the electric field on the surface of a
semiconductor wafer irradiated with the electron beam can be changed. For
example, if the inspection subject sample is a type of inspection subject
sample that tends to cause a discharge between itself and the objective
lens, a discharge especially in the via or around the via can be
prevented by changing the electric field by the electrode to reduce the
intensity of the electric field on the surface of the inspection subject
sample irradiated with the electron beam. Furthermore, since a discharge
between the via and the objective lens can be discharged, the pattern of
the semiconductor wafer or the like is never damaged with discharge.
Furthermore, since the potential given to the electrode is lower than the
charge given to the inspection subject sample, the intensity of the
electric field on the surface of the inspection subject sample irradiated
with the electron beam can be reduced, thus making it possible to prevent
a discharge to the inspection subject sample. Since the potential given
to the electrode is a negative potential, and the inspection subject
sample is grounded, the intensity of the electric field on the surface of
the inspection subject sample irradiated with the electron beam can be
reduced, thus making it possible to prevent a discharge to the inspection
subject sample.

[0790]Use of the control electrode for the purpose of preventing a
discharge has been mainly described, but the control electrode may be
used for screening energy of secondary electrons emitted from the wafer.
That is, if only secondary electrons having energy at a certain level or
greater, which have highest signal detection efficiency, are detected,
and so on, to obtain an image of high resolution, a predetermined
negative voltage can be applied to the control electrode, and the control
electrode can be used as a barrier of energy of secondary electrons.
Since a negative potential is applied to the control electrode, a force
repelling secondary electrons back to the sample is exerted. Secondary
electrons incapable of passing over this potential barrier go back to the
sample, and only secondary electrons passing over the potential barrier
are detected by the detector, thus making it possible to obtain an image
having a desired resolution.

2-7-2) Potential Application Method

[0791]In FIG. 92, a potential application mechanism 92•1 controls
generation of secondary electrons by applying a potential of several
volts to a mounting table of a stage on which the wafer is placed, based
on the fact that information of secondary electrons emitted from the
wafer depends on the potential of the wafer. Furthermore, this potential
application mechanism also plays a role to attenuate energy originally
possessed by irradiation electrons so that irradiation electron energy of
about 100 to 500 eV is applied to the wafer.

[0792]As shown in FIG. 92, the potential application mechanism 92•1
comprises a voltage application apparatus 92•4 electrically
connected to a holding surface 92•3 of a stage apparatus
92•2, and a charge-up examination and a voltage determination
system (hereinafter referred to as an examination and determination
system) 92•5. The inspection and determination system 92•5
comprises a monitor 92•7 electrically connected to an image
formation unit 92•6 of the detection system of the electro-optical
apparatus 13•8 (FIG. 13), an operator 92•8 connected to the
monitor 92•7, and a CPU 92•9 connected to the operator
92•84. The CPU 92•9 supplies signals to the voltage
application apparatus 92•4.

[0793]The potential application mechanism described above is designed to
search for a potential at which the wafer as an inspection object is hard
to be charged, and apply the potential.

[0794]A method for inspecting electric defects of the inspection sample
may use the fact the interest area has a different voltage in the case
where the interest area is electrically conductive with an originally
electrically insulated area.

[0795]Specifically, first, a charge is previously given to the sample to
cause a difference between the voltage of the originally electrically
insulated area and the voltage of the area that is originally
electrically insulated but becomes electrically conductive by some cause,
then the beam of the present invention is applied to acquire data of the
difference in voltage, and the acquired data is analyzed to detect that
the area is electrically conductive.

2-7-3) Electron Beam Calibration Method

[0796]In FIG. 93, an electron beam calibration mechanism 93•1
comprises a plurality of faraday cups 93•4 and 93•5 for
measurement of beam currents, placed at a plurality of locations on the
side part of a holding surface 93•3 of the wafer on a rotation
table 93•2. The faraday cup 93•4 is for a narrow beam (about
φ2 μm), and the faraday cup 93•5 is for a thick beam (about
φ2 μm). For the faraday cup 93•4 for a narrow beam, the
rotation table 93•2 is moved stepwise to measure a beam profile,
while for the faraday cup 93•5 for a thick beam, the total amount
of current of the beam is measured. The faraday cups 93•4 and
93•5 are arranged so that the upper surfaces are at the same level
of the upper surface of the wafer W placed on the holding surface
93•3. In this way, the primary electron beam emitted from the
electron gun is always monitored. This is because the electron gun cannot
always emit a constant electron beam, but the emission is changed with
time.

2-7-4) Cleaning of Electrode

[0797]When the electron beam apparatus of the present invention is
activated, a target material is floated by a proximity interaction
(charge of particles near the surface) and attracted to a high-pressure
area, and therefore organic materials are deposited on various electrodes
for use in formation and deflection of the electron beam. Insulating
materials that are gradually deposited with the charge of the surface
badly affect formation of the electron beam and the deflection mechanism,
and therefore the deposited insulating materials must be removed
periodically. The periodic removal of insulating materials is carried out
by producing plasmas of hydrogen, oxygen or fluorine and compounds
containing those elements such as HF, O2, H2O and
CMFN under vacuum using electrodes near the area on which
insulating materials are deposited, and keeping the plasma potential in a
space at a potential (several kVs, e.g. 20 V to 5 kV) at which spatters
occur on the surface of the electrode to oxidize, hydrogenise and
fluorinate only organic materials. Furthermore, by passing a gas having a
cleaning effect, contaminants on the surfaces of the electrode and the
insulator can be removed.

2-7-5) Alignment Control Method

[0798]An alignment control apparatus 94•1 of FIG. 94 is an apparatus
positioning the wafer W with respect to an electro-optical apparatus
94•2 using a stage apparatus, and performs control such as rough
adjustment of the wafer by a wide-field observation using an optical
microscope 94•3 (measurement under a lower magnification than
measurement by the electro-optical system), adjustment under a high
magnification using an electro-optical system of the electro-optical
apparatus 94•2, focus adjustment, setting of an inspection area,
pattern alignment. The reason why the wafer is inspected under a low
magnification using an optical system is that an alignment mark should be
easily detected with an electron beam when the pattern of the wafer is
observed to perform wafer alignment in a narrow-field using the electron
beam to automatically inspect the pattern of the wafer.

[0799]The optical microscope 94•3 is provided in a housing (may be
movably provided in the housing), and a light source (not shown) for
operating the optical microscope is housed. Furthermore, the
electro-optical system (primary optical system and secondary optical
system) of the electro-optical apparatus 94•2 is also used as an
electro-optical system for making an observation under a high
magnification. The outlined configuration thereof is shown in FIG. 94. To
observe an observation subject point on the wafer under a low
magnification, an X stage on the stage apparatus is moved in the X
direction to shift the observation subject point on the wafer to within
the field of view of the optical microscope. The wafer is visually
recognized in a wide field with the optical microscope 94•3, the
position of the wafer to be observed is displayed on a monitor 94•5
via a CCD 94•4, and the observation position is roughly determined.
In this case, the magnification of the optical microscope may be changed
from a low magnification to a high magnification.

[0800]Then, the stage apparatus is moved by a distance equivalent to an
interval δx between the optical axis of the electro-optical
apparatus 94•2 and the optical axis of the optical microscope
94•3 to shift the observation subject point on the wafer predefined
by the optical microscope to the position of the field of view of the
electro-optical apparatus. In this case, a distance δx between the
axial line O3-O3 of the electro-optical apparatus and the
optical axis O4-O4 of the optical microscope 94•3 (both
axes are deviated in position only along the direction of the X axis in
this embodiment, but may be deviated in position along the direction of
the Y axis and the direction of the Y axis) is already know, and
therefore movement of the stage apparatus by the value δx can shift
the observation subject point to the visually recognized position. After
the shift of the observation subject point to the visually recognized
position of the electro-optical apparatus is completed, the observation
subject point is SEM-imaged under a high magnification by the
electro-optical system, and the image is stored or displayed on a monitor
94•7 via a CCD 94•6.

[0801]After the observation point on the wafer is displayed on the monitor
under a high magnification with the electro-optical system in this way, a
positional deviation in the direction of rotation of the wafer with
respect to the center of rotation of the rotation table of the stage
apparatus, and a deviation δθ in the direction of rotation of
the wafer with respect to the optical axis O3-O3 of the
electro-optical system are detected, and a deviation in position in the X
and Y axes of a predetermined pattern with respect to the electro-optical
system is detected. The operation of the stage apparatus 94•8 is
controlled based on the detected value and separately obtained data of an
inspection mark provided on the wafer or data about the shape of the
pattern of the wafer to perform alignment of the wafer. The range of
alignment is within ±10 pixels in XY coordinates. It is preferably
within ±5 pixels, more preferably within ±2 pixels.

2-7-6) EO Correction

A. Overview

[0802]When the beam from the wafer is imaged with a TDI, the wafer should
be correctly positioned but actually, the wafer is placed on the X-Y
stage and mechanically positioned, and hence the accuracy is in the range
of several hundreds of nm to several tens of μm, and the response time
is several seconds to several milliseconds as practical values.

[0803]On the other hand, the design rule is refined toward several tens of
nm, and thus wiring with the line width of several tens of nm and vias
with the diameter of several tens of nm should be inspected to detect
their shape defects and electric defects, and dust with the diameter of
several tens of nm. Imaging dependent solely on the mechanical
positioning results in a significant difficulty in acquirement of a
correct image because the order of the response time and positioning
accuracy considerably differs from the order of the design rule and
imaging accuracy.

[0804]A sequence of imaging is carried out by a combination of a step (x
axis) and a constant speed scan (y axis), and relatively dynamic control
(y axis) generally has a large control residual, and thus is required to
be high level control for preventing a blur of an image.

[0805]In view of these items, an X-Y stage having high accuracy and
excellent responsivity is provided as a matter of course, but further a
function of EO correction is provided to achieve accuracy of control of
the beam for an imaging unit and a speed, which cannot be ensured by the
stage.

[0806]The fundamental method is such that the position of the wafer on the
stage is correctly recognized within a time delay of several micro
seconds in the order of sub nm with a laser interferometer and a bar
mirror placed on the x-y axis, a mechanical actuator is driven by an
automatic control loop, and the wafer is positioned at a target position
with a temporal delay and a residual. The control residual as a result of
positioning by this control is determined by a difference between the
target position generated within a control apparatus and the current
position obtained by a laser interferometer system. On the other hand,
the beam passes through various electrodes, and is then guided to an
imaging apparatus via a deflection electrode for correction. The
deflection electrode for correction has a sensitivity capable of
deflection within about several hundreds of μm, preferably within a
hundred μm, more preferably within several tens of μm equivalent to
the distance on the wafer, and by applying a voltage to the electrode,
the beam can be deflected to any position on a two-dimensional basis. The
control residual is subjected to calculation by a calculation apparatus,
and then converted into a voltage by a D/A converter, and the voltage is
applied to the deflection electrode for correction in a direction for
offsetting the residual. The above configuration makes it possible to
carry out correction close to the resolution of the laser interferometer.

[0807]As another method, the mean described above is used for the X axis
(step direction), and a transfer clock of the TDI as an imaging device is
transferred in synchronization with the speed of movement of the stage
for the Y axis.

[0808]The concept of EO correction is shown in FIG. 95. An indication
95•1 to a target position is outputted, and given to a control
feedback loop 95•2 including a mechanical actuator. This part
corresponds to a stage. The result of occurrence of a positional
displacement by driving is subjected to feedback by a position detector
95•3, and the positional displacement of a drive system converses
into the target position from the position indication, but a gain of a
control system is finite, and therefore a residual occurs. The current
position is detected in the order of sub nm by a position output system
95•4 (a laser interferometer is used here), a difference with the
position indication apparatus 95•1 is detected by a residual
detector 95•5, a voltage is applied to a deflection electrode
95•7 using a high-pressure and high-speed amplifier 95•6, a
voltage is applied in a direction for offsetting the residual, and if
this function is not originally provided, a function to reduce a
generated variation as denoted by reference numeral 95•8 to a
variation denoted by a reference numeral 95•9 is provided.

[0809]The specific configuration of devices is shown in FIG. 96. An XY
stage 96•1 drives the X axis with a servo motor 96•2 for
driving the X axis and an encoder 96•3, and detects a rough
position thereof and a speed to achieve smooth servo characteristics. In
this example, the servo motor is used, but a similar configuration can be
provided with an actuator such as a linear motor or ultrasonic motor.
Reference numeral 96•6 denotes a power amplifier for driving the
motor. Precise position information of the X axis achieves a position
detection function having a resolution in sub nm by a combination of a
mirror 96•7, an interferometer 96•8, a receiver 96•9, a
laser light source 96•10 and an interferometer board 96•11.

[0810]The Y axis functions similarly to the X axis orthogonal thereto, and
is comprised of a servo motor 96•12, an amplifier 96•13, a
mirror 96•14, an interferometer 9•5 and a receiver
96•16.

[0811]An X-Y stage controller 96•17 collectively controls these
devices, thereby enabling the stage to be moved two-dimensionally,
achieves accuracy of 1000 μm to 1 nm, preferably 100 μm to 2 nm,
more preferably 1 μm to 2 nm, further more preferably 0.1 μm to 2
nm, and achieves a performance such that the response time is several
thousands of milliseconds or less, preferably several tens of
milliseconds, more preferably several milliseconds. On the other hand, an
X reference value and a Y reference value are outputted from the X-Y
stage controller 96•17 to an EO corrector 96•18, position
information is outputted in a 32 bit binary format from the
interferometer 96•11, and the EO corrector 96•18 receives the
current position via a high-speed buffer board 96•19. Calculation
is internally performed, then a voltage is amplified with high-voltage
and high-speed amplifiers 96•20 and 96•21, then the voltage
is applied to a deflection electrode 96•22, and deflected for
correction of a residual, and an image information electron beam with a
positional deviation reduced to a minimum is guided to a TDI (imaging
device) 96•23. Reference numeral 96•24 denotes a portion for
generating a timing signal for determining a transfer speed of the TDI
96•23 as described later.

[0812]A function of generating a target position in the scan direction in
this apparatus will now be described. EO correction is a function of
determining a difference between the target position and the actual
position, deflecting the electron beam so as to offset the difference to
correct the position, but the correction range is limited to a range of
about several tens of μm. This is determined by an electrode
sensitivity, a dynamic range of the high-voltage and high-speed
amplifier, a noise level, and the number of bits of the D/A converter.
However, the actual position of the stage during scanning is considerably
deviated with respect to the target position, compared with the position
when the stage is stopped, due to the fact that the gain of the control
loop is finite. If the stage travels at 20 mm/s, the difference between
the actual position and the target position is about 400 μm, and the
correction range is considerably exceeded to saturate the system if the
difference is calculated and outputted directly.

[0813]To prevent such a phenomenon, this apparatus uses the following
means to avoid problems. The concept thereof is shown in FIG. 97.

[0814]A position 97•1 is the target position of the stage, and is
lineally incremented with time because the stage is moved at a constant
speed during scanning. On the other hand, a mechanical position
97•2 of the stage as a result of actually being controlled includes
mechanical vibrations of several microns and has a steady-state deviation
97•3 of about 400 μm. As a measure for removing this
steady-state deviation, it can be considered that a filter is used to
smooth position information when the stage travels but in this case,
there is a disadvantage that a delay absolutely occurs due to a time
constant of the filter, and if a time constant such that a ripple is
negligible is provided, a measurement starting area is strictly limited,
leading to a considerable increase in overall measurement time. Thus, in
this proposal, for detecting this steady-state deviation, at least a
difference between the current position at the time of previous scanning
and the target position is integrated at least about 216 times, the
resulting value is divided by the number of samples to determine an
average value 97•4 of the steady-state deviation between the target
position and the current position, and calculation is performed as a
target position 97•6 synthesized by subtracting an average value
97•4 from a target position 97•5 during present scanning to
achieve a configuration enabling EO correction to be performed within the
dynamic range as shown by 98•1 of FIG. 98. Furthermore, the number
of integrations are not limited to this value, but may be a smaller
number of integration stages as long as a target level of accuracy is
obtained.

[0815]FIG. 99 is a block diagram. A current position 99•2 is
subtracted from a target value 99•1, and the integration
calculation is carried out within a block of 99.3 during scanning. On the
other hand, the average value of the steady-state deviation previously
determined in the same manner is outputted to a position 99•3 from
a position 99•4. The position 99•4 is subtracted from the
target value 99•1 to obtain a synthesized target position
99•6 by a subtractor 99•5, and this value is subtracted from
a current position 99•7 from an interferometer to achieve EO
correction data free from a delay in response and a ripple.

[0816]FIG. 100 shows a structure of detection of an average of a
difference of a block of 99•3 in FIG. 99. Integration is carried
out by an ALU 100•1 and a latch 100•2, a word of a data
selector 100•4 is selected by a value of a cumulative time counter
100•3, calculation equivalent to division is carried out, and an
average value of the steady-state deviation is outputted.

[0817]An idea of a transfer clock of the TDI is shown in FIG. 101. The TDI
is an imaging device having photo-electric elements connected in a
multiple stage in the scan direction, and transmitting charges of imaging
devices to subsequent devices to improve the sensitivity and reduce
random noises, but as shown in FIG. 101, it is important that imaging
objects on the stage correspond to pixels on the TDI on a one-to-one
basis, and if this relation is broken, an image is blurred. Synchronous
relations are shown in FIGS. 1-1, 1-2, 2-1 and 2-2, and asynchronous
relations are shown in FIGS. 3-1, 3-2, 4-1 and 4-2. Since the TDI is
transferred to a next stage in synchronization with an external pulse,
this is achieved by generating a transfer pulse when the stage is moved
in an amount equivalent to one pixel.

[0818]However, the output of position information in a laser
interferometer that is in the mainstream takes a form of outputting a 32
bit binary output in synchronization with its own internal clock of 10
MHz, and thus this cannot be easily achieved in the original state.
Furthermore, if the resolution is several tens of nm, the accuracy of the
transfer pulse is also important, and thus high-speed and high-accuracy
digital processing is required. A method devised in the invention is
shown in FIG. 102. In this figure, position information of the
interferometer and a synchronization signal of 10 MHz are introduced into
a main circuit via a buffer 102•1. A 10 MHz clock 102•2
generates a clock of 100 MHz synchronized with a PLL 102•3, and
supplies the same to each circuit. Calculation processing is carried out
for every 10 states of this synchronization signal 102•4. Present
position information is retained in a latch 102•5, and a pervious
value is retained in a latch 102•6. A difference between both the
values is calculated by an ALU 102•7, and a difference of positions
for every 10 states is outputted from a component 102•8. This
difference value is loaded to a parallel serial comparator 102•9 as
a parallel value, and outputted from an OR 102•10 as a number of
serial pulses in synchronization with the clock of 100 MHz. A comparator
102•11 has a similar function, but is configured to be capable of
operating continuously for every 10 states in combination with components
102•12 and 102•13. As a result, a serial pulse matching a
position difference is outputted from a summation circuit 102•10 to
a counter 102•14 for every 10 MHz. Provided that the resolution of
the laser interferometer is 0.6 nm and one pixel has a size of 48 nm, 19
pulses are outputted at the time when the counter becomes equivalent to
one pixel if a comparator 102•15 is set at 80. Use of this signal
as a transfer pulse from outside the TDI allows an operation synchronized
with even a variation in stage speed, thus making it possible to prevent
blurring.

[0819]A timing chart is shown in FIG. 103. Reference numeral 1 denotes
interferometer coordinate (position) information, in which numbers show
positions as examples. Reference numeral 2 denotes a synchronization
signal of 100 MHZ created by a PLL. A bank A is operation timing of the
parallel serial converter 102•9, and a bank B is operation timing
of the comparator 102•11. After latch timing 7 for storing position
information, difference calculation timing 8 is executed, a value is
loaded to the parallel serial converter 102•9, time of one cycle of
a next 10 M clock 3 is used to execute an output of 4. The bank B carries
out a similar operation in timing delayed by one cycle of the 10 M clock
3 to achieve pulse generation of 6 without difficulties.

2-7-7) Image Comparison Method

[0820]FIG. 104 shows the outlined configuration of a defect inspection
apparatus according to an alteration example of the present invention.
The defect inspection apparatus is the projection type inspection
apparatus described above, and comprises an electron gun 104•1
emitting a primary electron beam, an electrostatic lens 104•2
deflecting and shaping the emitted primary electron beam, an E×B
deflector 104•3 deflecting the shaped primary electron beam so that
the primary electron beam impinges upon the semiconductor wafer W at
almost a right angle in a field where an electric field E and a magnetic
filed B are orthogonal, an objective lens 104•4 making the
deflected primary electron beam form an image on the wafer W, a stage
104•5 provided in a sample chamber (not shown) capable of being
evacuated and movable in a horizontal plane with the wafer W placed
thereon, an electrostatic lens 104•6 of a projection system
magnifying and projecting a secondary electron beam and/or a reflection
electron beam emitted from the wafer W with irradiation of the primary
electron beam under a predetermined magnification to form an image, a
detector 104•7 detecting the formed image as a secondary electron
image of the wafer, and a control unit 104•8 controlling the entire
apparatus, and carrying out processing for detecting defects of the wafer
based on the secondary electron image detected by the detector
104•7. Furthermore, not only secondary electrons but also scattered
electrons and reflection electrons contribute to the secondary electron
image described above, but it is called a secondary electron image
herein.

[0821]Furthermore, a deflection electrode 104•9 deflecting with the
electric field or the like an angle at which the primary electron beam
enters the wafer is provided between the objective lens 104•4 and
the wafer W•A deflection controller 104•10 controlling the
electric field of the deflection electrode is connected to the deflection
electrode 104•9. The deflection controller 104•10 is
connected to the control unit 104•8, and controls the deflection
electrode so that an electric field matching a command from the control
unit 104•8 is generated in the deflection electrode 104•9.
Furthermore, the deflection controller 104•10 can be formed as a
voltage control apparatus controlling a voltage given to the deflection
electrode 104•9.

[0822]The detector 104•7 may have any configuration as long as the
secondary electron image formed by the electrostatic lens 104•6 can
be converted into a signal capable of being subjected to post-processing.
For example, as shown in detail in FIG. 62, the detector 104•7 may
comprise a micro-channel plate 62•1, a fluorescent screen
62•2, a relay optical system 62•3, and an imaging sensor
62•4 constituted by a large number of CCD elements. The
micro-channel plate 62•1 has a large number of channels in a plate,
and further generates a large number of electrons while secondary
electrons made to form an image by the electrostatic lens 104•6
pass through the channels. That is, secondary electrons are amplified.
The fluorescent screen 62•2 converts secondary electrons into light
by emitting fluorescence with amplified secondary electrons. The relay
lens 62•3 guides the fluorescence to the CCD imaging sensor
62•4, and the CCD imaging sensor 62•4 converts an intensity
distribution of secondary electrons on the surface of the wafer W into an
electric signal for each element, i.e. digital image data, and outputs
the same to the control unit 104•8. Here, the micro-channel plate
62•1 may be omitted and in this case, blurring caused by expansion
between the micro-channel plate 62•1 and the fluorescent screen can
be reduced. For example, an image of 0.2 in MTF can be enhanced to
0.3-0.6.

[0823]The control unit 104•8 may be constituted by a general
personal computer or the like as illustrated in FIG. 104. This computer
comprises a control unit main body 104•11 for various kinds of
control and calculation processing according to a predetermined program,
a CRT 104•12 displaying the result of processing by the main body
104•11, and an input unit 104•13 such as a keyboard and a
mouse for an operator to input instructions. Of course, the control unit
104•8 may be constituted by hardware dedicated to defect inspection
apparatus, a workstation or the like.

[0824]The control main body 104•11 is comprised of a CPU, a RAM, a
ROM, a hard disk, various kinds of control boards such as a video board,
and the like (not shown). A secondary electron image storage area
104•14 for storing electric signals received from the detector
104•7, i.e. digital image data of the secondary electron image of
the wafer W is assigned onto a memory of a RAM or hard disk. Furthermore,
a reference image storage unit 104•15 for storing in advance
reference image data of the wafer having no defects exists on the hard
disk. Furthermore, in addition to a control program for controlling the
entire defect inspection apparatus, a defect detection program
104•16 for reading secondary electron image data from the storage
area 104•14 and automatically detecting defects of the wafer W
according to a predetermined algorithm based on the image data is stored
on the hard disk. As describe in detail later, this defect detection
program 104•16 has a function that the reference image read from
the reference image storage unit 104•15 and an actually detected
secondary electron image are made to match each other to automatically
detect defective areas, and if it is determined that defects exist,
warning display is provided to the operator. At this time, a secondary
electron image 104•17 may be displayed on a display unit of the CRT
104•12.

[0825]The action of the defect inspection apparatus according to the
embodiment will now be described using flowcharts of FIGS. 105 to 107 as
an example. First, as shown in the flow of a main routine of FIG. 105,
the wafer W as an inspection object is set on the stage 104•5 (step
105•1). A large number of wafers stored in a loader may be all set
on the stage 104•5 on one-by-one basis as described previously.

[0826]Then, images of a plurality of inspection subject areas mutually
displaced and partially overlapping on the XY plane of the surface of the
wafer W are each acquired (step 105•2). The plurality of inspection
subject areas, images of which are to be acquired, are, for example,
rectangular areas denoted by reference numerals 108•2a,
108•2b, . . . , 108•2k, . . . on a wafer inspection surface
108•1, and it can be understood that these areas are mutually
displaced while partially overlapping around an inspection pattern
108•3 of the wafer. For example, as shown in FIG. 109, images
109•1 (inspection subject images) of 16 inspection subject areas
are acquired. Here, in the image shown in FIG. 109, a rectangular cell
corresponds to one pixel (or may be a block unit larger than a pixel),
and black-painted cells correspond to an image area of the pattern on the
wafer W. The details of the step 105•2 will be described later with
the flowchart of FIG. 106.

[0827]Then, image data of the plurality of inspection subject areas
acquired at step 105•2 are each compared with reference image data
stored in the storage unit 104•15 (step 105•3 in FIG. 105) to
determine whether or not defects exist on the wafer inspection surface
covered by the plurality of inspection object areas. In this step,
processing of so called matching between image data is carried out, and
the details thereof will be described later with the flowchart of FIG.
107.

[0828]If it is determined that defects exist on the wafer inspection
surface covered by the plurality of inspection subject areas (positive
determination in step 105•4) as a result of comparison at step
105•3, the operator is warned of existence of defects (step
105•5). As a method for warning, for example, a message indicating
existence of defects is displayed on the display unit of the CRT
104•12, and an enlarged image 104•17 of a pattern having
defects may be displayed at the same time. The defective wafer may be
immediately taken out from the sample chamber, and stored at a storage
site different from that for the wafer having no defects (step
105•6).

[0829]If it is determined that the wafer W has no defects (negative
determination in step 105•4) as a result of comparison at step
105•5, whether any area to be inspected still exists or not is
determined for the wafer W that is currently an inspection object (step
105•7). If an area to be inspected still exists (positive
determination in step 105•7), the stage 104•5 is driven to
move the wafer W so that other area to be inspected next is included in
the area of irradiation with the primary electron beam (step
105•8). Then, processing returns to step 105•2, where the
same processing is repeated for the other inspection area.

[0830]If no area to be inspected exists (negative determination in step
105•7), or after the step of taking out the defective wafer (step
105•6), whether the wafer W that is currently an inspection object
is a last wafer or not, i.e. whether or not any wafer that has not been
inspected yet still exists on a loader (not shown) is determined (step
105•9). If the wafer W is not a last wafer (negative determination
in step 105•9), the inspected wafer is stored at a predetermined
storage site and instead, a new wafer that has not been inspected is set
on the stage 104•5 (step 105•10). Then, processing returns to
step 105•2, where the same processing is repeated for the wafer. If
the wafer W is the last wafer (positive determination in step
105•9), the inspected wafer is stored at the predetermined storage
site to complete all the steps. An identification number is assigned to
each cassette or each wafer, and the wafer being inspected is recognized
and monitored to prevent duplicated inspection of a wafer, for example.

[0831]The flow of processing at step 105•2 will now be described
according to the flowchart of FIG. 106. In this figure, first, an image
number I is set to an initial value 1 (step 1061). The image number is an
identification number assigned sequentially to each of a plurality of
inspection subject area images. Then, an image position (Xi,
Yi) is determined for the inspection subject area of the set image
number i (step 106•2). This image position is defined as a
specified position in the area for demarcating the inspection subject
area, for example a central position of the area. At present, the image
position is (X1, Y1) because i equals 1, this corresponds to,
for example, the central position of an inspection subject area
108•2a shown in FIG. 108. The image positions of all inspection
subject image areas are defined in advance, and are stored on the hard
disk of the control unit 104•8, for example, and read at step
106•2.

[0832]Then, the deflection controller 104•10 applies a potential to
the deflection electrode 104•9 so that the primary electron beam
passing through the deflection electrode 104•9 of FIG. 104 is
applied to the inspection subject image area of the image position
(Xi, Yi) determined at step 106•2 (step 106•3 of
FIG. 106).

[0833]Then, the primary electron beam is emitted from the electron gun
104•1, and applied to the surface of the set wafer W through the
electrostatic lens 104•2, the E×B deflector 104•3, the
objective lens 104•4 and the deflection electrode 104•9 (step
106•4). At this time, the primary electron beam is deflected by an
electric field produced by the deflection electrode 104•9, and
applied over the entire inspection subject image area at the image
position (Xi, Yi) on the wafer inspection surface 108•1.
If the image number equals 1, the inspection subject area is an area
108•2a.

[0834]Secondary electrons and/or reflection electrons (hereinafter
referred to as only "secondary electrons") are emitted from the
inspection subject area of irradiation with the primary electron beam.
Then, the generated secondary electron beam is made to form an image on
the detector 104•7 under a predetermined magnification by the
electrostatic lens 104•6 of an enlargement projection system. The
detector 104•7 detects the secondary electron beam made to form an
image, and converts the image into an electric signal or digital image
data for each detecting element and outputs the same (step 106•5).
Detected digital image data with the image number of i is transferred to
the secondary electron image storage area 104•14 (step
106•6).

[0835]Then, the image number i is incremented by 1 (step 106•7), and
whether the incremented image number (i+1) exceeds a fixed value
iMAX or not is determined (step 106•8). This value iMAX
is the number of inspection subject images to be acquired, and equals
"16" in the example of FIG. 109 described above.

[0836]If the image number i does not exceed the fixed value iMAX
(negative determination in step 106•8), processing returns to step
106•2, where the image position (Xi+1, Yi+2) is
determined again for the incremented image number (i+1). This image
position is a position obtained by shifting the image from the image
position (Xi, Yi) determined in the pervious routine in the X
direction and/or Y direction by a predetermined distance (ΔXi,
ΔYi). In the example of FIG. 108, the inspection subject area
is at a position (X2, Y2) obtained by shifting the image from
(Xi, Yi) only in the Y direction, which corresponds to a
rectangular area 108•2b shown by a broken line. Furthermore, the
values of (ΔXi, ΔYi) (i=1, 2, . . . iMAX) may
be defined as appropriate based on data of how a pattern 108•3 of
the wafer inspection surface 108•1 is actually shifted empirically
from the field of view of the detector 104•7, and the number and
area of inspection subject areas.

[0837]Processing at steps 106•2 to 106•7 is carried out one
after another repeatedly for iMAX inspection subject areas. As shown
in FIG. 108, these inspection subject area are mutually shifted in
position while partially overlapping on the wafer inspection surface
108•1 so that an image position (Xk, Yk) is obtained by
making k shifts. In this way, 16 inspection subject image data
illustrated in FIG. 109 are captured in the image storage area
104•14. It can be understood that an image (inspection subject
image) 109•1 of the acquired plurality of inspection subject areas
has partially or fully captured therein an image 109•2 of the
pattern 108•3 on the wafer inspection surface 108•1.

[0838]If the incremented image number i exceeds iMAx (positive
determination in step 106•8), this subroutine is returned, and
processing proceeds to a comparison step.

[0839]Furthermore, image data memory-transferred at step 106•6
consists of the intensity value of secondary electrons for each pixel (so
called solid data) detected by the detector 104•7, but may be
stored in the storage area 104•14 with the image data subjected
various calculation processing because the image data is subjected to
matching calculation with a reference image at the subsequent comparison
step (step 105•3). Such calculation processing includes, for
example, normalization processing for making the size and/or density of
image data match the size and/or density of reference image data, and
processing of removing as a noise an isolated group of images having a
predetermined number or smaller number of pixels. Further, instead of
simple solid data, data may be compressed and converted into a feature
matrix with a feature of a detection pattern extracted within the bounds
of not reducing the detection accuracy of a precise pattern. Such feature
matrixes include, for example, an m×n feature matrix having as each
component the total of secondary electron intensity values of pixels (or,
normalized value obtained by dividing the total value by the total number
of pixels of the entire inspection subject area) included in each of
m×n blocks (m<M, n<N) into which a two-dimensional inspection
subject area consisting of M×N pixels is divided. In this case,
reference image data is also stored in the same form. The image data
cited in the embodiments of the present invention includes not only mere
solid data but also image data feature-extracted with any algorithm as
described above.

[0840]The flow of processing at step 105•3 will now be described
according to the flowchart of FIG. 107. First, the CPU of the control
unit 104•8 reads reference image data from the reference image
storage unit 104•15 (FIG. 104) onto a working memory of a RAM or
the like (step 107•1). This reference image is denoted by reference
numeral 109•3 in FIG. 109. The image number i is set to 1 (step
107•2), and inspection subject image data with the image number of
i is read from the storage area 104•14 onto the working memory
(step 107•3).

[0841]Then, the read reference image data is made to match the data of the
image i to calculate a distance value Di between both the data (step
107•4). This distance value Di indicates similarity between
the reference image and the inspection subject image i, which means that
the larger the distance value, greater the difference between the
reference image and the inspection subject image. Any quantity indicating
similarity may be employed as the distance value Di. For example, if
image data consists of M×N pixels, the secondary electron intensity
(or feature amount) of each pixel may be considered as each vector
component of a M×N-dimensional space, and a Euclidean distance or a
coefficient of correlation between a reference image vector and an image
i vector on the M×N-dimensional space may be calculated. Of course,
a distance other than the Euclidean distance, for example, so called an
urban area distance or the like may be calculated. Further, if a large
number of pixels exist, the calculation amount considerably increases,
and therefore the distance value between image data expressed by the
m×n feature vector may be calculated as described above.

[0842]Then, whether the calculated distance value Di is smaller than
a threshold value Th or not is determined (step 107•5). This
threshold value Th is determined empirically as a reference when whether
the reference image sufficiently matches the inspection subject image is
determined. If the distance value Di is smaller than the
predetermined threshold value Th (positive determination in step
107•5), it is determined that "no defect exits" on the inspection
surface 1034 of the wafer W (step 107•6), and this sub routine is
returned. That is, if even only one of inspection subject images
approximately matches the reference image, it is determined that "no
defect exists". In this way, it is not necessary that the reference image
should be matched with all inspection subject images, thus making it
possible to make a determination quickly. In the example of FIG. 109, it
can be understood that the inspection subject image of third line and
third row approximately matches the reference image with no shift in
position with respect to the reference image.

[0843]If the distance value Di is equal to or larger than the
predetermined threshold value Th (negative determination in step
107•5), the image number i is incremented by 1 (step 107•7),
and whether the incremented image number (i+1) exceeds the fixed number
iMAX or not is determined (step 107•8).

[0844]If the image number i does not exceed the fixed value iMAX
(negative determination in step 107•8), processing returns to step
107•3, where image data is read for the incremented image number
(i+1), and the same processing is repeated.

[0845]If the image number i exceeds the fixed value iMAX (positive
determination in step 107•8), it is determined that "defects exit"
on the inspection surface 1034 of the wafer W (step 107•9), and
this sub routine is returned. That is, if none of inspection subject
images approximately match the reference image, it is determined that
"defects exist".

[0846]Each embodiment of the stage apparatus has been described above, but
the present invention is not limited to the above examples, and may be
altered arbitrarily and appropriately within the substance of the present
invention.

[0847]For example, the semiconductor wafer W is used as an inspection
subject sample, but the inspection subject sample of the present
invention is not limited thereto, and any sample allowing defects to be
detected with an electron beam can be selected. For example, a mask or
the like provided with a pattern for light exposure for the wafer may be
used as an inspection object.

[0848]Furthermore, the present invention can be applied not only to
apparatuses detecting defects using charged particle beams other than
electrons, but also to any apparatus capable of acquiring images allowing
defects of samples to be inspected.

[0849]Further, the deflection electrode 104•9 may be placed not only
between the objective lens 104•4 and the wafer W, but also at any
position as long as the area of irradiation with the primary electron
beam can be changed. For example, it may be placed between the E×B
deflector 104•3 and the objective lens 104•4, between the
electron gun 104•1 and the E×B deflector 104•3, or the
like. Further, by controlling a field generated by the E×B
deflector 104•3, the direction of deflection may be controlled.
That is, the E×B deflector 104•3 may also have a function as
the deflection electrode 1049.

[0850]Furthermore, in the embodiment described above, any one of matching
between pixels and matching between feature vectors is performed when
performing matching between image data, but both types of matching may be
combined. For example, compatibility between enhancement of the speed and
accuracy can be achieved by two-stage processing such that first,
high-speed matching is performed with feature vectors having small
calculation amounts and as a result, for high-similarity inspection
subject images, matching is performed with more precise pixel data.

[0851]Furthermore, in the embodiment of the present invention, a
positional shift of the inspection subject image is coped with only by
shifting the position of the area of irradiation with the primary
electron beam, but processing of searching for an optimum matching area
on image data before or during matching processing (detecting areas of
high coefficients of correlation and performing matching between the
areas) may be combined with the present invention. According to this, a
large positional shift of the inspection subject image can be coped with
by shifting the position of the area of irradiation with the primary
electron beam according to the present invention, and also a relatively
small positional shift can be absorbed in subsequent digital image
processing, thus making it possible to improve the accuracy of defect
detection.

[0852]Further, the configuration in FIG. 104 has been shown as an electron
beam apparatus for defect detection, but the electro-optical system and
the like can be altered arbitrarily and appropriately. For example,
electron beam irradiating means (104•1, 104•2, 104•3)
of the defect inspection apparatus shown in FIG. 104 has a form such that
the primary electron beam is made to enter the surface of the wafer W
uprightly from above, but the E×B deflector 104•3 may be
omitted, and the primary electron beam may be made to enter the surface
of the wafer W slantingly.

[0853]Furthermore, the flow of the flowchart of FIG. 105 is not limited to
the examples described above. For example, for a sample for which it is
determined that defects exist at step 105•4, defect inspection in
other areas is not carried, but the flow of processing may be changed so
that defects are detected covering all areas. Furthermore, if the area of
irradiation with the primary electron beam is expanded so that almost all
inspection areas of the sample can be covered with one irradiation, steps
105•7 and 105•8 may be omitted.

[0854]As described in detail above, according to the defect inspection
apparatus of this embodiment, images of a plurality of inspection subject
areas mutually displaced while partially overlapping on the sample are
each acquired, and the images of the inspection subject areas are
compared with the reference image to inspect defects of the sample, thus
making it possible to obtain an excellent effect such that a reduction in
accuracy of defect inspection resulting from a positional shift between
the inspection subject image and the reference image can be prevented.

[0855]Further, according to the device production process of the present
invention, defect inspection of the sample is carried out using the
defect inspection apparatus described above, thus making it possible to
obtain an excellent effect such that the yield of products can be
improved and defective products can be prevented from being dispatched.

2-7-8) Device Production Process

[0856]The embodiment of a process for producing a semiconductor device
according to the present invention will now be described with reference
to FIGS. 110 and 111. FIG. 110 is a flowchart showing one embodiment of
the process for producing a semiconductor device according to the present
invention. The production process of this embodiment includes the
following main steps.

(1) Wafer production step of producing a wafer (or wafer preparation step
of preparing a wafer) (step 110•1).(2) Mask production step of
producing a mask for use in light exposure (or mask preparation step of
preparing a mask) (step 110•2).(3) Wafer processing step of
subjecting the wafer to necessary process processing (step
110•3).(4) Chip assembly step of cutting out chips formed on the
wafer on one-by-one basis and making the chips operable (step
1110•4).(5) Chip inspection step of inspecting the assembled chips
(step 110•5).

[0857]Furthermore, the main steps described above each consist of several
sub-steps. It is the wafer processing step (3) among these main steps
that has decisive influences on the performance of the semiconductor
device. In this step, designed circuit patterns are stacked on the wafer
one after another to form a large number of chips operating as memories
and MPUs. This wafer processing step includes the following steps.

(A) Thin film formation step of forming a dielectric thin film and a
wiring portion serving as an insulating layer or a thin metal film
forming an electrode portion (using CVD, spattering or the like).(B)
Oxidization step of oxidizing the thin film layer and the wafer
substrate.(C) Lithography step of forming a resist pattern using a mask
(reticle) for selectively processing the thin film layer, the wafer
substrate and the like.(D) Etching step of processing the thin film layer
and the substrate according to the resist pattern (e.g. using a dry
etching technique).(E) Ion/impurity injection and diffusion step.(F)
Resist peeling step.(G) Step of inspecting the processed
wafer.Furthermore, the wafer processing step is repeated for a necessary
number of layers to produce a semiconductor device operating as designed.

[0858]FIG. 111 is a flowchart showing the lithography step lying at the
heart of the wafer processing step. The lithography step includes the
following steps.

(a) Resist coating step of coating a resist on the wafer having the
circuit pattern formed at the previous step (step 111•1).(b) Step
of exposing the resist to light (step 111•2).(c) Development step
of developing the exposed resist to obtain a pattern of the resist (step
111•3).(d) Annealing step for stabilizing the developed resist
pattern (step 111•4).

[0859]The semiconductor device production step, the wafer processing step
and the lithography step described above are well known, and thus are not
required to be described further in detail.

[0860]If the defect inspection process and defect inspection apparatus
according to the present invention are used in the inspection step (G),
even a semiconductor device having a fine pattern can be inspected in
high throughput, and therefore 100% inspection can be performed, thus
making it possible to improve the yield of products and prevent defective
products from being dispatched.

2-7-9) Inspection

[0861]Inspection procedures in the inspection step of (G) will be
described using FIG.

[0862]112. Generally, the defect inspection apparatus using electron beams
is expensive, and has low throughput compared to other process
apparatuses, and is thus used, at present, after an important step
considered to require most strictest inspection (e.g. etching, film
formation, CMP (chemical-mechanical polishing) flatness processing,
etc.), or in a more precise wiring step part, i.e. 1 to 2 steps of the
wiring step and the gate wiring step as a pervious step in the case of
the wiring step. Particularly, it is important that shape defects and
electric defects of wiring having a design rule of 100 nm or less, i.e. a
line width of 100 nm or less, a via hole having a diameter of 100 nm or
less and the like are found, and fed back to the process.

[0863]The wafer to be inspected is aligned on a very precise X-Y stage
through an atmosphere transportation system and a vacuum transportation
system, then fixed by an electrostatic chuck mechanism or the like, and
then subjected to defect inspection according to procedures (of FIG.
112). First, the position of each die is checked and the height of each
site is detected as necessary by an optical microscope, and the results
are stored. In addition thereto, the optical microscope acquires
microscopic images of areas required to be observed such as defects, and
the microscopic images are used for comparison with electron beam images.
Then, the conditions of the electro-optical system are set, and the
electro beam image is used to modify information set with the optical
microscope to improve the accuracy.

[0864]Then, information of a recipe appropriate to the type of wafer
(immediately preceding step, whether the wafer size is 200 mm or 300 mm,
and the like) is inputted to the apparatus, followed by setting the
inspection site, the electro-optical system, inspection conditions and
the like, and then defect inspection is carried out usually in real time
while acquiring an image. Comparison between cells and die comparison are
carried out by a high-speed information processing system having
algorithms, and the results are outputted to a CRT and the like and
stored in a memory as necessary.

[0865]Defects include particle defects, shape abnormalities (pattern
defects) and electric defects (breakage and poor conduction of wiring or
vias, etc.), and these defects can be identified, and defects can be
automatically classified in real time on the basis of the size of the
defect and whether or not the defect is a killer defect (serious defect
resulting in an unusable chip, etc.). Particularly, the process is
effective in classifying the defects of wiring having a line width of 100
nm or less, a via having a diameter of 100 nm or less and the like.
Detection of electric defects is achieved by detecting a contrast
abnormality. For example, the site of poor conduction is usually charged
positively and has a contrast reduced by irradiation with the electron
beam (about 500 eV), and thus can be differentiated from a normal site.
The electron beam irradiating means in this case refers to low-potential
(energy) electron beam generating means (generation of thermal electrons,
UV/photoelectrons) provided for clarifying the contrast by the difference
in potential, aside from electron beam irradiating means for usual
inspection. Before irradiating the electron beam for inspection to the
inspection object area, this low-potential electron beam (having energy
of 100 eV or less, for example) is generated/applied. In the case of the
projection system in which the inspection site can be positively charged
only by irradiating an electron beam for inspection, it is not necessary
to provide separately low-potential electron beam generating means
depending on specifications. Furthermore, defect inspection can be
carried out using a difference in contrast caused by application of a
positive or negative potential to a sample such as a wafer with respect
to the reference potential or the like (caused by a difference in
flowability depending on the forward direction or inverse direction of
the element).

[0866]The contrast by a difference in potential may be converted into an
image of a signal effective for displaying potential contrast data and
then displayed. The potential contrast image can be analyzed to identify
a structure at a voltage higher or lower than an expected value, i.e.
poor insulation or poor conduction and defects. For example, potential
contrast images are acquired from different dies on the wafer,
respectively, and differences between the images are detected to
recognize defects. Furthermore, image data equivalent to the potential
contrast image of the inspection subject die is generated from design
data such as CAD data, and a difference between this image data and the
potential contrast image acquired from the inspection subject die on the
wafer is detected to recognize defects.

[0867]The process can be used in a line width measurement apparatus and
measurement of matching accuracy. Information of the wafer to be
inspected, for example the number of the cassette and the number of the
wafer (or lot number) is all stored and managed as to the current
position and sate of the wafer. Thus, there arises no trouble of
erroneously performing inspection twice or performing no inspection.

2-8) Inspection process

2-8-1) Overview

[0868]The basic flow of inspection is shown in FIG. 113. First, after
transportation of the wafer including an alignment operation 113•1,
a recipe specifying conditions and the like related inspection
(113•2). At least one recipe are required for the inspection
subject wafer, but a plurality of recipes may exist for one inspection
subject recipe for coping with a plurality of inspection conditions.
Furthermore, if there are a plurality of wafers having the same pattern,
the plurality of wafers may be inspected with one recipe. A path
1113•3 of FIG. 113 indicates that creation of the recipe is not
required immediately before the inspection operation if inspection is
carried out with a recipe created in the past in this way. Subsequently,
in FIG. 113, an inspection operation 113•4 carries out inspection
according to conditions and sequences described in the recipe. Defect
extraction is carried out immediately each time a defect is found during
the inspection operation, and the following operations are carried out
almost in parallel:

a) operation of classifying defects (113•5) and adding extracted
defect information and defect classification information to a result
output file;b) operation of adding an extracted defect image to an image
dedicated result output file or file; andc) operation of displaying
defect information such as a position of an extracted defect on an
operation screen.

[0869]When inspection is completed for each inspection subject wafer, the
following operations are carried out almost in parallel:

a) operation of closing and storing the result output file;b) operation of
sending the inspection result if the inspection result is requested by
external communication; andc) operation of discharging the wafer.

[0870]If a setting for continuously inspecting wafers is made, a next
inspection subject wafer is conveyed, and the series of operations
described above are repeated.

[0871]The flow of FIG. 113 will be described further in detail below.

(1) Creation of Recipe

[0872]The recipe is a set file for conditions and the like relating to
inspection, and can be stored. The recipe is used to make a setting of
apparatus during inspection or before inspection, the conditions relating
to inspection described in the recipe are as follows:

[0873]For the setting of inspection object die among these conditions, the
operator designates dies to be inspected with respect to a die map screen
displayed on the operation screen as shown in FIG. 114. In the example of
FIG. 114, a die 1 on the end face of the wafer and a die 2 judged as an
apparently defective die 2 in the previously step are grayed out and
omitted from the inspection object, and remaining dies are defined as
inspection object dies. Furthermore, a function of automatically
designating inspection dies based on a distance from the end face of the
wafer and pass/fail information of dies detected in the previous step is
also provided.

[0874]Furthermore, to set inspection areas within the die, the operator
designates inspection areas with an input device such as a mouse based on
images acquired with an optical microscope or EB microscope, with respect
to an in-die inspection area setting screen displayed on the operation
screen, as shown in FIG. 115. In the example of FIG. 115, an area
115•1 indicated by a solid line and an area 115•2 indicated
by a broken line are set.

[0875]The area 115•1 has almost an entire area of the die as a set
area. An adjacent die comparison method (die-die inspection) is used as
the inspection algorithm, and the details of detection conditions and
observation conditions for this area are set separately. For the area
115•2, array inspection (inspection) is used as the inspection
algorithm, and the details of detection conditions and observation
conditions are set separately. That is, a plurality of inspection areas
can be set, and a unique inspection algorithm and inspection sensitivity
can be set for each inspection area. Furthermore, one inspection area can
be superimposed on the other, and the same area can be processed with
different inspection algorithms at a time.

(2) Inspection Operation

[0876]For inspection, the inspection subject wafer is finely divided into
certain scan widths and scanned as shown in FIG. 116. The scan width
approximately depends on the length of a line sensor, but the end
portions of line sensors slightly overlap one another. This is for the
purpose of evaluating continuity between lines when detected defects are
finally subjected to integration processing, and providing allowance for
alignment of images when comparison inspection is carried out. The
overlap amount thereof is about 16 dots for the line sensor of 2048 dots.

[0877]The scan direction and sequence are schematically shown in FIG. 117.
That is, a two-way operation A for reduction of inspection time, a
one-way operation B due to mechanical limitation, or the like can be
selected by the operator.

[0878]Furthermore, a function of automatically calculating an operation
for reducing the scan amount based on the setting of inspection object
dies in the recipe to carry out inspection is also provided. FIG. 118-1
shows an example of scanning where there is one inspection die
118•1, in which unnecessary scans are not performed.

2-8-2) Inspection Algorithm

[0879]Algorithms of inspection carried out by this apparatus are
classified broadly into the following two types:

[0880]1. array inspection (cell inspection); and

[0881]2. random inspection (die inspection).

As shown in FIG. 118-2, the die is separated into a cell portion
118•2 having a cycle structure that is used mainly for a memory,
and a random portion 118•3 having no cycle structure. The cell
portion 118•2 having a cycle structure is capable of being
inspected by comparison between cells in the same die because a plurality
of comparative objects exist in the same die. On the other hand, the
random portion 118•3 requires comparison between dies because there
is no comparative object in the same die. Random inspection is further
classified as follows according to comparative objects:

[0885]A method generally called as a golden template method refers to the
methods b) and c), and the reference die is a golden-template on the
reference die comparison method, while CAD data is a golden template in
the CAD data comparison method.

[0886]The operation of each algorithm will be described below.

2-8-2-1) Array Inspection (Cell Inspection)

[0887]Array inspection is applied for inspection of the cycle structure. A
DRAM cell or the like is one example thereof.

[0888]For inspection, a reference image as a reference is compared with an
inspection subject image, and a difference thereof is extracted as a
defect. The reference image and the inspection subject image may be
binary images or multi-value images for improvement of detection
accuracy.

[0889]The defect may be the difference itself between the reference image
and the inspection subject image, but a secondary determination for
prevention of erroneous detection may be made based on difference
information such as the amount of detected difference and the total area
of images having the difference.

[0890]In array inspection, the reference image is compared with the
inspection subject image in a structure cycle unit. That is, images
collectively acquired with the CCD or the like may be compared in one
structure cycle unit while reading the images, or if the reference image
has n structure cycle units, n structure cycle units may be compared at a
time.

[0891]One example of a method for generating a reference image is shown in
FIG. 119. Here, an example of comparison in one structure cycle unit is
described, and thus generation of one structure cycle unit is shown. The
number of cycles can be set to n in the same method.

[0892]As a premise, the inspection direction is a direction A in FIG. 119.
Furthermore, a cycle 4 is an inspection subject cycle. The magnitude of
the cycle is inputted by the operator watching the image, and therefore
cycles 1 to 6 can easily be recognized in FIG. 119.

[0893]A reference cycle image is generated by adding cycles 1 to 3
immediately before the inspection subject cycle in each pixel. Even if
defects exist in any of cycles 1 to 3, influences thereof are not
significant because equalization processing is performed. This generated
reference cycle image is compared with an inspection subject cycle image
4 to extract defects.

[0894]When an inspection subject cycle image 5 is then inspected, cycles 2
to 4 are added and averaged to generate a reference cycle image.
Subsequently, an inspection subject cycle image is similarly generated
from images obtained before acquirement of the inspection subject cycle
image to continue inspection.

2-8-2-2) Random Inspection (Die Inspection)

[0895]Random inspection can be applied without being limited by the
structure of the die. For inspection, a reference image as a reference is
compared with an inspection subject image, and a difference thereof is
extracted as a defect. The reference image and the inspection subject
image may be binary images or multi-value images for improvement of
detection accuracy. The defect may be the difference itself between the
reference image and the inspection subject image, but a secondary
determination for prevention of erroneous detection may be made based on
difference information such as the amount of detected difference and the
total area of images having the difference. Random inspection can be
classified based on how the reference image is determined. The operation
will be described below.

A. Adjacent Die Comparison Method (Die-Die Inspection)

[0896]A reference image is a die adjacent to an inspection subject die.
The inspection subject image is compared with two dies adjacent thereto
to make a determination on defects. That is, in FIGS. 120 and 121, the
method has the following steps in a situation in which a switch
121•4 and a switch 121•5 are set so that a memory 121•1
and a memory 121•2 of an image processing apparatus are connected
to a path 121•41 from a camera 121•3:

a) step of storing a die image 1 in the memory 121•1 from the path
121•41 along a scan direction S;b) step of storing a die image 2 in
the memory 121•2 from the path 121•41;c) acquiring the die
image 2 from the path 121•42 while carrying out the step b), and at
the same time comparing the acquired die image 2 with image data stored
in the memory 121•1, having the same relative position in the die,
to determine a difference;d) step of storing the difference determined in
the step c);e) step of storing a die image 3 in the memory 121•1
from the path 121•41;f) acquiring the die image 3 from the path
121•42 while carrying out the step c), and at the same time
comparing the acquired die image 3 with image data stored in the memory
121•1, having the same relative position in the die, to determine a
difference;g) step of storing the difference determined in the step f);h)
step of making a determination on defects of the die image 2 from the
results stored in the steps d) and g); andi) step of repeating steps a)
to h) in subsequent continuous dies.

[0897]By setting, before determining the difference in steps c) and f),
position alignment of compared two images by setting: correction that is
carried out so that a difference in position is eliminated; or density
alignment: correction that is carried out so that a difference in density
is eliminated; or both position alignment and density alignment may be
performed.

B. Reference Die Comparison Method (Die-any Die Inspection)

[0898]A reference die is designated by the operator. The reference die is
a die existing on the wafer, or a die image stored before inspection, and
the reference die is first scanned or transferred, and the image is
stored in a memory as a reference image. That is, in FIGS. 121 and 122,
the method has the following steps:

a) step of selecting a reference die from dies of the inspection subject
wafer or die images stored before inspection by the operator;b) step of
setting the switch 121•4 and the switch 121•5 so that at
least one of the memory 121•1 and the memory 121•2 of the
image processing apparatus are connected to the path 121•41 from
the camera 121•3, if the reference die exists on the inspection
subject wafer;c) step of setting the switch 121•4 and the switch
121•5 so that at least one of the memory 121•1 and the memory
121•2 of the image processing apparatus are connected to a path
121•7 from a memory 121•6 having a reference image as a die
image stored therein, if the reference die is a die image stored before
inspection;d) step of scanning the reference die and transferring the
reference image as a reference die image to the memory of the image
processing apparatus, if the reference die exists on the inspection
subject wafer;e) step of transferring the reference image as a reference
die image to the memory of the image processing apparatus without
necessity to perform scanning, if the reference die is a die image stored
before inspection;f) step of comparing an image obtained by sequentially
scanning the inspection subject image, the image in the memory to which
the reference image as a reference die image is transferred, and image
data having the same relative position in the die to determine a
difference;g) step of making a determination defects from the difference
obtained at step f); andh) step of inspecting the same area with respect
to the scan position of the reference die and the die origin of the
inspection subject die for the entire wafer continuously as shown in FIG.
124, and repeating the steps d) to g) while changing the scan position of
the reference die until the entire die is inspected.

[0899]By setting, before determining the difference in step f), position
alignment of compared two images by setting: correction that is carried
out so that a difference in position is eliminated; or density alignment:
correction that is carried out so that a difference in density is
eliminated; or both position alignment and density alignment may be
performed.

[0900]The reference die image stored in the memory of the image processing
apparatus at the step d) or e) may be the entire reference die, or may be
inspected while being updated as part of the reference die.

C. CAD Data Comparison Method (CAD Data-Any Die Inspection)

[0901]In the step of production of a semiconductor shown in FIG. 123, a
comparison image is created from CAD data being an output of a step of
designing a semiconductor pattern with CAD and the comparison image is
defined as a reference image. The reference image may be an image of the
entire die or part of the die including an inspection area.

[0902]Furthermore, the CAD data is usually vector data, and cannot be used
as a comparison image unless the data is converted into raster data
equivalent to image data equivalent to image data obtained by a scanning
operation. In this way, the following conversions are carried out for CAD
data processing work.

a) Vector data being CAD data is converted into raster data.b) The
conversion a) is carried out in a unit of image scan width obtained by
scanning the inspection subject die during inspection.c) The conversion
b) converts an image to be obtained by scanning the inspection subject
die and image data having the same relative position in the die.d) The
conversion c) is carried out with inspection scanning and conversion work
overlapping one another.

[0903]The conversions a) to d) are examples of conversion in an unit of
image scan width for enhancement of the speed, but scanning can be
performed even if the conversion unit is not fixed to the image scan
width. Furthermore, the method has at least one of the following
functions as an additional function for work of converting vector data
into raster data:

a) function of processing raster data into a multiple value;b) function of
setting a gray scale weight and an offset in the processing into a
multiple value in view of the sensitivity of the inspection apparatus
with respect to the function a); andc) function of carrying out image
processing for subjecting pixels to processing such as expansion and
contraction after converting vector data into raster data.

a) step of converting CAD data into raster data with a calculator 1, and
generating a comparison image with the additional function and storing
the comparison image in the memory 121•6;b) step of setting the
switch 121•4 and the switch 121•5 so that at least one of the
memory 121•1 and the memory 121•2 of the image processing
apparatus are connected to the path 121•7 from the memory
121•6;c) step of transferring the comparison image of the memory
121•6 to the memory of the image processing apparatus;d) step of
comparing an image obtained by sequentially scanning the inspection
subject image, the image in the memory to which the comparison image is
transferred, and image data having the same relative position in the die
to determine a difference;e) step of making a determination defects from
the difference obtained at step d); andf) step of inspecting the same
area of the inspection subject die over the entire wafer with the scan
position of the reference die as a comparison image continuously as shown
in FIG. 124, and repeating steps a) to e) while changing the scan
position of the reference die until the entire die is inspected.

[0905]By setting, before determining the difference in step d), position
alignment of compared two images by setting: correction that is carried
out so that a difference in position is eliminated; or density alignment:
correction that is carried out so that a difference in density is
eliminated; or both position alignment and density alignment may be
performed.

[0906]The reference die image stored in the memory of the image processing
apparatus at step c) may be the entire reference die, or may be inspected
while being updated as part of the reference die.

2-8-2-2') Method for Carrying Out Cell Inspection and Die Inspection at
the Same Time

[0907]The algorithms of array inspection (cell inspection) and random
inspection for inspecting the cycle structure have been described, but
cell inspection and die inspection can be carried out at the same time.
Specifically, the cell portion and the random portion are processed
separately, and a comparison is made between cells in the die for the
cell portion, while a comparison with an adjacent die, the reference die
or CAD data is made for the random portion. This allows inspection time
to be considerably reduced, resulting in an improvement in throughput.

[0908]Furthermore, in this case, it is preferable that inspection circuits
of the cell portion are individually independently provided. Furthermore,
if inspection is not carried out at the same time, it is also possible to
provide one inspection circuit, wherein a setting is made so that the
switch can be made between software for cell inspection and random
inspection, and comparison inspection is carried out by switching of
software. That is, if inspection of a pattern is carried out using
algorithms for a plurality of operations, different circuits may be
prepared for the algorithms to carry out inspection at a time, or
algorithms matching those operations may be provided to carry out
inspection with the switch made between the algorithms with one circuit.
In any case, the present invention can be applied even if the type of the
cell portion is complicate, and a comparison is made between cells for
this type of cell portion, and a comparison is made between dies or
between the die and CAD data for the random portion.

2-8-2-3) Focus Mapping

[0909]The basic flow of a focus function is shown in FIG. 125. First,
after transportation of the wafer including the alignment operation, a
recipe specifying conditions and the like relating to inspection is
created. There is a focus map recipe as one of such recipes, and
auto-focusing is performed during the inspection operation and the review
operation according to focus information specified in the recipe.
Procedures for creating the focus map recipe and operational procedures
of auto-focusing will be described below.

Procedures for Creating Focus Map Recipe

[0910]The focus map recipe has an independent input screen in this
example, and the operator carries out the following steps to create the
recipe, but the recipe may be added to an input screen provided for a
different purpose.

a) Step of inputting focus map coordinates such as a die position in which
a focus value is inputted, and a pattern in the die. Switch 126•1
in FIG. 126.b) Step of setting a die pattern required when the focus
value is automatically measured.

[0911]This step may be skipped if the focus value is not automatically
measured.

c) Step of Setting the Best Focus Value of the Focus Map Coordinates
Determined at Step a).

[0912]At step a), the operator may designate any die, but all dies may be
selected, or dies may be selected for every n dies. Furthermore, in the
input screen, the operator may select either a diagram schematically
showing a die arrangement or an image using a real image.

[0913]At step c), a selection/setting is made in a mode in which the
operator manually sets a value with a focus switch 126•2 associated
with the voltage value of an electrode for focusing (switch 126•3
in FIG. 126) or a mode in which the focus value is automatically
determined (switch 126•4 in FIG. 126).

a) obtaining an image of focus position Z=1 and calculating a contrast
thereof;b) carrying out the procedure a) for Z=2, 3, 4.c) determining a
contrast function with regression from the contrast values obtained in
the procedures a) and b) (FIG. 127); andd) calculating Z providing a
maximum value of the contrast function and setting the maximum value to
the best focus value.

[0916]For example, the die pattern required when the focus value is
automatically measured shows a good result if a line & space shown in
FIG. 128 is selected, but the contrast can be measured irrespective of
the shape as long as a black-and-white pattern is provided.

[0917]By carrying out the procedures a) to d), the best focus value of one
point is determined. The data format at this time is (X, Y, Z), wherein
XY is coordinates with which the focus is determined, Z is a set of the
best focus value, and the focus map coordinate number (X, Y, Z)
determined with the focus map recipe exists. This is called a focus map
file as part of the focus map recipe.

[0918]Operational Procedures of Auto-Focusing

[0919]The method for setting the focus to the best focus during the
inspection operation of acquiring images from the focus map recipe and
the review operation comprises the following steps.

a) Position information is subdivided based on a focus map file 1 created
during creation of the focus map recipe, the best focus at this time is
calculated, and a subdivided focus map file 2 is created;b) The
calculation of step a) is performed with an interpolation function;c) The
interpolation function of step b) is linear interpolation, spline
interpolation or the like, which is designated by the operator during
creation of the focus map recipe.d) The XY position of the stage is
monitored to change the voltage of the electrode for focusing to a focus
value suitable for the current XY position, described in the focus map
file 2.

[0920]To describe the procedures more specifically, in FIG. 129, the black
circle corresponds to focus values of the focus map file 1, and the white
circle corresponds to focus values of the focus map file 2, wherein

1. intervals between focus values of the focus map file are interpolated
with focus values of the focus map file, and2. the focus position Z is
changed according to scanning to maintain the best focus value and at
this time, for the interval between focus map files (white circles), a
value is retained up to a position at which the value is changed.

2-8-2-4) Litho-Margin Measurement

[0921]Embodiments relating to litho-margin measurement will be described
below.

(1) Embodiment 10

Litho-Margin Measurement 1

Overview

[0922]1. The range of conditions for a light-exposure machine and best
conditions are determined. The target is the focus.2. This embodiment is
a method of application of inspection apparatus, and is not limited to
the electron beam mapping method and the scanning method. That is, the
method using light, the electron beam method, and any combination of such
methods with the mapping method or scanning method may be used.3.
Application of Reference Die Comparison Method (Die-Any Die inspection)

[0923]FIG. 130 shows a flow showing the operation of the embodiment 1. The
embodiment will be described based on this figure.

[0924]At step 130•1, conditions are changed to two dimensionally
expose the surface of the wafer to light using focus conditions and
exposure time conditions as parameters as shown in FIG. 131 as an
example. Furthermore, an image pattern of one shot=1 die is used.

[0925]Many stepper light-exposure machines have a function of
automatically changing the parameter to perform light-exposure, generally
called TEST exposure, and this function may be used directly.

[0926]At step 130•2, steps of development, resist peeling, etching,
CVD, CMP, plating and the like may be carried out, and particularly in
observation with the electron beam, the resist is charged and is thus
hard to be observed, and therefore steps of development, resist peeling
and plating are carried out. Resist observation is desirable.

[0927]Details of step 130•3 will be described with FIG. 132. In this
step, using a function of measuring a contrast of an image set by the
operator of the inspection apparatus carrying out step 130•4, the
minimum line & space portion of the die pattern is recorded as an area
where the contrast is measured, and the following work is conducted.

[0928]First, an upper limit Db and a lower limit Da of exposure time are
determined. For exposure time equal to or greater than Db and exposure
time equal to or less than Da, the contrast value is extremely low, and
thus such exposure time is excluded from inspection (grayed-out part in
FIG. 132).

[0929]Then, an upper limit Fb and a lower limit Fa of the focus value are
determined. For any focus value equal to or greater than Fb and any focus
value equal to or smaller than Fa, the contrast value is extremely low,
and thus such focus values are excluded from inspection (grayed-out part
in FIG. 133).

[0930]Then, a die at intersection of a row of dies Ds in the middle
between Da and Db and a row of dies Fs in the middle between Fa and Fb is
selected as a best exposure condition shot. The step of selecting the
best exposure condition shot is all carried out automatically.

[0931]At step 130•4, inspection is carried out by the reference die
comparison method (Die-Any Size inspection) with the reference die as a
comparison image and with white dies as inspection subject dies in FIG.
132.

[0932]At step 130•5, a determination is made on exposure conditions
using the inspection result in step 130•4. That is, an effect is
used such that if exposure conditions are not appropriate, for example,
the line and space of the die pattern are not resolved, or the edge
portion of the pattern has an obtuse angle, so a difference occurs
between the reference image and the inspection subject image, resulting
in detection as pattern defects. Of course, pattern defects and particles
caused by erroneous exposure, not caused by exposure conditions, may be
detected, but in this case, inspection is carried out again. However, the
frequency of occurrence of such a case is so low in terms of probability
that no problem arises.

[0933]Specific procedures of the step 130•5 are as follows.

1) Because higher priority is given to determination of a focus margin,
exposure time is fixed at Ds in FIG. 132, and a relation between the
focus value and the number of defects is determined (FIG. 133).2) At this
time, the criterion for determination on the focus value is such that no
defect occurs due to exposure conditions, and therefore focus values
acceptable as exposure conditions are values in the range of F1 to F2 as
a conclusion.3) For the type of value/unit of expression in the
light-exposure machine which F1 and F2 specifically have, it can be
easily calculated by transferring the position of the die and its
exposure conditions through a communication path connected from the
light-exposure machine via RS232C or Ethernet. The apparatus has a
function of converting the value into a value capable of being directly
inputted to the exposure machine and displaying together with a function
of pass/fail determination as exposure conditions.4) Furthermore, if a
dedicated communication path or a communication path of SEMI standard or
the like is used, the result by this inspection apparatus can be fed back
to the light-exposure machine. The above procedures are further carried
out with exposure conditions (exposure time) changed to determine the
margin of focus and exposure.

(2) Embodiment 11

Litho-Margin Measurement 2

Overview

[0934]The range of conditions for a light-exposure machine and best
conditions are determined. The target is the focus.

1. This embodiment is a method of application of inspection apparatus, and
is not limited to the electron beam mapping method and the scanning
method. The optical method, the electron beam method, and combinations of
such methods with the mapping method or scanning method may be used.

[0935]FIG. 134 shows a flow showing the operation of the embodiment 2. The
embodiment will be described based on this figure.

[0936]At step 134•1, conditions are changed to two dimensionally
expose the surface of the wafer to light using focus conditions and
exposure time conditions as parameters as shown in FIG. 135 as an
example. Furthermore, an image pattern of one shot=1 die is used.

[0937]Many stepper light-exposure machines have a function of
automatically changing the parameter to perform light-exposure, generally
called TEST exposure, and this function may be used directly.

[0938]At step 134•2, steps of development, resist peeling, etching,
CVD, CMP, plating and the like may be carried out, and particularly in
observation with the electron beam, the resist is charged and is thus
hard to be observed, and therefore steps of development, resist peeling
and plating are carried out. Preferably, the step is ended with
observation at the level of the resist.

[0939]At step 134•3, a reference image required to have best
conditions where possible is generated from CAD data having an exposed
shot pattern. At this time, raster data as image data is processed into a
multiple value. As shown in FIG. 136, in patterns having different line
widths, for example a pattern A, a pattern B and a pattern C, the pattern
C is finer than the pattern B, but when a comparison is made for the
level of white of the pattern empirically, the level of white of the
pattern C is closer to black than that of the pattern B, and when a
comparison is made for the level of black of the pattern, the level of
black of the pattern C is closer to white than that of the pattern B.
Thus, image data is processed into a multiple value in consideration of
not just two values, one appearing black and the other appearing white as
an image, but the shape and fineness of the pattern, the pattern position
on the wafer and the like.

[0940]Furthermore, in consideration of setting conditions of the
observation system and influences of charge-up, magnetic fields and the
like at the same time, image data generated from CAD data is subjected to
image processing such that a difference is not recognized as pseudo
defects when an image obtained by actual observation is compared with
image data generated from CAD data.

[0941]At step 134•4, the image generated at step 134•3 is
defined as a comparison image, dies on the wafer are defined as
inspection subject images, and die comparisons are made to carry out
inspection.

[0942]At step 134•5, a determination is made on exposure conditions
using the inspection result at step 134•4. That is, an effect is
used such that if exposure conditions are not appropriate, for example,
the line and space of the die pattern are not resolved, or the edge
portion of the pattern has an obtuse angle, so a difference occurs
between the reference image and the inspection subject image, resulting
in detection as pattern defects. Of course, pattern defects and particles
caused by erroneous exposure, not caused by exposure conditions, may be
detected, but in this case, inspection is carried out again. However, the
frequency of occurrence of such a case is so low in terms of probability
that no problem arises.

[0943]Specific procedures of the step 134•5 are as follows.

1) Because higher priority is given to determination of a focus margin,
exposure time is set to an empirically obtained fixed value, and a
relation between the focus value and the number of defects in this case
is determined (FIG. 137).2) At this time, the criterion for determination
on the focus value is such that no defect occurs due to exposure
conditions, and therefore focus values acceptable as exposure conditions
are values in the range of F1 to F2 as a conclusion.3) For the type of
value/unit of expression in the light-exposure machine which F1 and F2
specifically have, it can be easily calculated by transferring the
position of the die and its exposure conditions through a communication
path connected from the light-exposure machine via RS232C or Ethernet.
The apparatus has a function of converting the value into a value capable
of being directly inputted to the exposure machine and displaying
together with a function of pass/fail determination as exposure
conditions.4) Furthermore, if a dedicated communication path or a
communication path of SEMI standard or the like is used, the result by
this inspection apparatus can be fed back to the light-exposure machine.

[0944]The litho-margin measurement of exposure conditions has been
described above, a reticle or stencil mask as a mask for exposure may be
inspected. In this case, inspection for determination of exposure
conditions can be simplified.

3. Other Embodiments

3-1) Alteration example of stage apparatus

[0945]FIG. 138 shows one alteration example of stage apparatus in a
detection apparatus of the present invention.

[0946]A partition plate 138•4 largely protruding almost horizontally
in the +Y direction and -Y direction (lateral direction in FIG. 139) is
mounted on the upper face of a Y direction movable portion 138•2 of
a stage 138•1, and a diaphragm portion 138•5 having a small
conductance is always formed between the partition plate 138•4 and
the upper face of an X direction movable portion 138•4.
Furthermore, a similar partition plate 138•6 is formed on the upper
face of the X direction movable portion 138•4 in such a manner as
to protrude in the +X direction (lateral direction in (A) of FIG. 138),
and a diaphragm portion 138•8 is always formed between the
partition plate 138•6 and the upper face of a stage table
138•7. The stage table 138•7 is fixed on the bottom wall in a
housing 138•9 by a well known method.

[0947]Accordingly, the diaphragm portions 138•5 and 138•8 are
always formed irrespective of the position to which a sample table
138•10 moves, and therefore if gas is emitted from guide surfaces
138•11 and 138•12 when the movable portions 138•2 and
138•4 move, movement of emitted gas is prevented by the diaphragms
138•5 and 138•8, thus making it possible to considerably
reduce an increase in pressure of a space 138•13 near the sample to
which a charged beam is applied.

[0948]Grooves for differential exhaust shown in FIG. 140 are formed around
a static pressure bearing 138•14 on the side face and lower face of
the movable portion 138•2 of the stage and the lower face of the
movable portion 138•4, and the apparatus is evacuated through the
grooves, and therefore if the diaphragm portions 138•5 and
138•8 are formed, emitted gas from the guide surface is mainly
discharged by the differential exhaust portions. Accordingly, the
pressures of spaces 138•15 and 138•16 within the stage are
higher than the pressure within a chamber C. Thus, by additionally
providing sites to be evacuated not just evacuating the spaces
138•15 and 138•16 through differential exhaust grooves
140•1 and 140•2, the pressures of the spaces 138•15 and
138•16 can be reduced, and an increase in pressure of the space
138•13 near the sample can be reduced to a lower level. Evacuation
channels 138•17 and 138•18 for this purpose are provided. The
evacuation channel extends through the stage table 138•7 and the
housing 138•9 to outside a housing 138•9. Furthermore, the
evacuation channel 138•18 is formed in the X direction movable
portion 138•4, and extends through the lower face of the X
direction movable portion 138•4.

[0949]Furthermore, if the partition plates 138•3 and 138•6 are
placed, the chamber should be upsized so that the chamber and the
partition plate do not interfere with each other, but this can be
improved by employing a flexible material or structure for the partition
plate. In this embodiment, it can be considered that the partition plate
is formed by a rubber or formed into a bellow shape, and the end portion
in the traveling direction is fixed to the X direction movable portion
138•4 for the partition plate 138•3, and fixed to the inner
wall of the housing 138•9 for the partition plate 138•6.
Furthermore, reference numeral 138•19 denotes a column.

[0950]FIG. 141 shows a second alteration example of stage apparatus. In
this aspect, a cylindrical partition 141•2 is formed around the end
portion of a column or a charged beam irradiating portion 141•1 so
that a diaphragm is provided between the partition and the upper face of
a sample W. In this configuration, even if gas is emitted from the XY
stage to increase the pressure within the C chamber, a space 141•3
inside the partition is partitioned by the partition 141•2 and
evacuated through a vacuum tube 141•4, and therefore a difference
in pressure is produced between the space within the chamber C and the
space 141•3 inside the partition, so that the increase in pressure
of the space 141•3 inside the partition can be reduced to a low
level. The size of a gap between the partition 141•2 and the
surface of the sample depends on the level at which the pressures within
the chamber C and around the irradiation area 141•1 are kept, but
is appropriately several tens of μm to several mm. Furthermore, the
partition 141•2 is made to communicate with the vacuum tube by a
well known method.

[0951]Furthermore, in a charged beam irradiation apparatus, there are
cases where a high voltage of about several kilovolts is applied to the
sample W, and a discharge may be caused if a conductive material is
placed near the sample. In this case, if an insulating material such as
ceramics is used for the material of the partition 141•2, no
discharge is caused between the sample W and the partition 141•2.

[0952]Furthermore, a ring member 141•5 placed around the sample W
(wafer) is a platy adjustment part fixed on a sample table 141•6,
and is adjusted to have a height equal to that of the wafer so that very
small gaps 141•7 are formed over the entire circumference of the
leading end portion of the partition 141•2 even if a charged beam
is applied to a sample such as a wafer. Consequently, irrespective of the
position of the wafer W to which the charged beam is applied, constant
very small gaps 952 are always formed at the leading end portion of the
partition 141•2, thus making it possible to stably keep the
pressure of the space 141•3 around the leading end portion of the
column.

[0953]Another alteration example is shown in FIG. 142. A partition
142•1 including a differential exhaust structure is provided around
the charged beam irradiating portion 141•2 of the column
138•19. The partition 142•1 has a cylindrical shape, a
circular groove 142•2 is formed therein, and an evacuation channel
142•3 extends upward from the circular groove. The evacuation
channel is connected to a vacuum tube 142•5 via an internal space
142•4. A very small gap of about several tens of μm to several
mm is formed between the lower end of the partition 142•1 and the
upper face of the sample W.

[0954]In this configuration, even if gas is emitted from with movement of
the stage to increase the pressure within the chamber C, and the gas
flows into the leading end portion or charged beam irradiating portion
141•2, the partition 142•1 reduces the gap between itself and
the sample W to considerably diminish the conductance, so that the gas is
hindered from flowing into the leading end portion and thus the amount of
inflow is reduced. Further, the gas flowing into the portion is exhausted
from the circular groove 142•2 to the vacuum tube 142•5, and
thus little gas flows into a space 141•6 around the charged beam
irradiating portion 141•2, thus making it possible to keep the
pressure in the charged beam irradiating portion 141•2 at a desired
vacuum.

[0955]Still another alteration example is shown in FIG. 143. a partition
143•1 is provided around the chamber C and the charged beam
irradiating portion 141•1 to isolate the charged beam irradiating
portion 141•1 from the chamber C. The partition 143•1 is
coupled to a freezer 143•3 via a support member 143•2 made of
material having a high thermal conductivity such as copper or aluminum,
and is cooled to about -10° C. to -200° C. A member
143•4 is intended for hindering thermal conduction between the
cooled partition 143•1 and the column 138•19, and is made of
material having a low thermal conductivity such as ceramics or resin
material. Furthermore, a member 143•5 is made of non-insulating
material such as ceramics, and is formed at the lower end of the
partition 143•1 to prevent the sample W and the partition
143•1 from causing a discharge.

[0956]Owing to this configuration, gas molecules flowing from the chamber
into the charged beam irradiating portion is hindered from flowing into
the charged beam irradiating portion by the partition 143•1, or
frozen and collected on the surface of the partition 143•1 even if
they flow into the portion, thus making it possible to keep the pressure
of the charged beam irradiating portion 143•6 at low level.

[0957]Furthermore, for the freezer, various freezers such as cooling with
liquid nitrogen, a He freezer and a pulse tube-type freezer may be used.

[0958]Still another alteration example is shown in FIG. 144. Partition
plates 144•1 and 144•2 are provided on both the movable
portions of the stage as in the case of the configuration shown in FIG.
138, and a space 144•4 and the chamber C are partitioned via
diaphragms 144•5 and 144•6 by these partitions even if a
sample table 144•3 moves to any position. Further, a partition
144•7 similar to that shown in FIG. 141 is formed around the
charged beam irradiating portion 141•1, and the chamber C and a
space including the charged beam irradiating portion 141•1 are
partitioned via a diaphragm 144•8. Thus, even if gas adsorbed on
the stage is emitted into the space 144•4 to increase the pressure
of this area during movement of the stage, an increase in pressure of the
chamber C is reduced to a low level, and an increase in pressure of a
space 144•9 is reduced to a lower level. Consequently, the pressure
of the charged beam irradiation space 144•9 can be kept at a low
level. Furthermore, the partition 142•1 including a differential
exhaust mechanism as shown in the partition 144•7 is used, or a
partition cooled by a freezer as shown in FIG. 142 is used, whereby the
space 144•9 can be stably kept at a lower pressure.

[0959]According to these embodiments, the following effects can be
exhibited.

(1) The stage apparatus can exhibit a accurate positioning performance
under vacuum, and the pressure at the charged beam irradiation position
is hard to increase. That is, the sample can be accurately processed with
a charged beam.(2) Gas emitted from the static-pressure bearing support
portion can hardly pass through the partition to the charged beam
irradiation area side. In this way, the vacuum at the charged beam
irradiation position can be further stabilized.(3) Emitted gas is hard to
pass to the charged beam irradiation area side, and thus the vacuum in
the charged beam irradiation area can be easily maintained with
stability.(4) The inside of the vacuum chamber is divided into a charged
beam irradiation chamber, a static-pressure bearing chamber and an
intermediate chamber via a small conductance. A vacuum pumping system is
formed such that the charged beam irradiation chamber, the intermediate
chamber and the static-pressure bearing chamber are arranged in ascending
order of pressure. Variations in pressure in the intermediate chamber are
further reduced, and variations in pressure in the charged beam
irradiation chamber are further reduced by one more partition, thus
making it possible to reduce variations in pressure to a level causing
substantially no problem.(5) An increase in pressure when the stage is
moved can be reduced to a low level.(6) An increase in pressure when the
stage is moved can be reduced to a lower level.(7) An inspection
apparatus having a high performance in positioning of the stage and
having a stabilized degree of vacuum of the charged beam irradiation area
can be achieved, thus making it possible to provide an inspection
apparatus having a high inspection performance and not contaminating the
sample.(8) A light-exposure apparatus having a high performance in
positioning of the stage and having a stabilized degree of vacuum of the
charged beam irradiation area can be achieved, thus making it possible to
provide a light-exposure apparatus having a high exposure accuracy and
not contaminating the sample.(9) A semiconductor is produced by an
apparatus having a high performance in positioning of the stage and
having a stabilized degree of vacuum of the charged beam irradiation
area, whereby a fine semiconductor circuit can be formed.

[0960]Furthermore, it is apparent that the stage apparatus of FIGS. 138 to
144 can be applied to the stage 13•6 of FIG. 13.

[0961]Another embodiment of the XY stage according to the present
invention will be described with reference to FIGS. 145 to 147.
Furthermore, in the example of the conventional technique and embodiment
of FIG. 148, like reference numerals are given to common components.
Furthermore, the "vacuum" means a vacuum called in the art, and does not
necessarily refer to an absolute vacuum.

[0962]Another embodiment of the XY stage is shown in FIG. 145. The leading
end portion of a column 145•1 irradiating a charged beam to a
sample, i.e. a charged beam irradiating portion 145•2 is attached
to a housing 145•3 sectioning a vacuum chamber C. The sample W
placed on a table movable in the X direction (lateral direction in FIG.
145) of an XY stage 145•4 is placed just below the column. The
charged beam can be applied accurately to any position on the surface of
the sample W by the high-accurate XY stage 145•4.

[0963]A seat 145•5 of the XY stage 145•4 is fixed on the
bottom wall of the housing 145•3, and a Y table 145•6 moving
in the Y direction (direction perpendicular to the plane in FIG. 145) is
placed on the seat 145•5. Raised portions protruding into recessed
grooves formed on a pair of Y direction guides 145•7 and
145•8 placed on the seat 145•5 on the side facing the Y table
are formed on both side faces (left and right side faces in FIG. 145) of
the Y table 145•6. The recessed groove extends in the Y direction
over almost the entire length of the Y direction guide. Static-pressure
bearings 145•9, 145•10, 145•11 and 145•12 each
having a well known structure are provided on the upper and lower faces
and the side faces, respectively, of the raised portion protruding into
the recessed groove, and by blowing high-pressure gas via these
static-pressure bearings, the Y table 145•6 is supported on the Y
direction guides 145•7 and 145•8 in a non-contact manner, and
can smoothly reciprocate in the Y direction. Furthermore, a linear motor
145•13 having a well known structure is placed between the seat
145•5 and the Y table 145•6, and drive in the Y direction is
performed by the linear motor. High-pressure gas is supplied to the Y
table through a flexible tube 145•14 for supply of high-pressure
gas, and high-pressure gas is supplied to the static-pressure bearings
145•10 and 145•9 and 145•12 and 145•11 through a
gas channel (not shown) formed in the Y table. The high-pressure gas
supplied to the static-pressure bearings is ejected into a gap of several
microns to several tens of microns formed between opposite guide surfaces
of the Y direction guide to correctly position the Y table in the X
direction and Z direction (vertical direction in FIG. 145) with respect
to the guide surface of the Y table.

[0964]An X table 145•14 is placed on the Y table such that it is
movable in the X direction (lateral direction in FIG. 145). On the Y
table 145•6, a pair of X direction guides 145•15
(145•16) (only X direction guide 145•15 is shown) having the
same structure as those of the Y direction guides 145•7 and
145•8 for the Y table are provided with the X table 145•14
held therebetween. A recessed groove is formed on the X direction guide
on the side facing the X table, and a raised portion protruding into the
recessed groove is formed on the side part (side part facing the X
direction guide) of the X table. The recessed groove extends over almost
the entire length of the X direction guide. Static-pressure bearings (not
shown) similar to the static-pressure bearings 145•9, 145•10,
145•17, 145•11, 145•12 and 145•18 are provided in
a similar arrangement on the upper and lower faces and the side faces of
the X direction table 145•14 protruding into the recessed groove. A
linear motor 145•19 having a well known structure is placed between
the Y table 145•6 and the X table 145•14, and the X table is
driven in the X direction by the linear motor. High-pressure gas is
supplied to the X table 145•14 through a flexible tube
145•20, and high-pressure gas is supplied to the static-pressure
bearing. This high-pressure gas is ejected from the static-pressure
bearings to the guide surface of the X direction guide, whereby the X
table 145•14 is accurately supported on the Y direction guide in a
non-contact manner.

[0965]The vacuum chamber C is evacuated through vacuum tubes 145•21,
145•22 and 145•23 connected to a vacuum pump or the like
having a well known structure. The tubes 145•22 and 145•23 on
the inlet side (inner side of vacuum chamber) extend through the seat
145•5, and form on the upper face thereof openings near the
position at which the high-pressure gas is discharged from the XY stage
145•4, and prevent an increase in pressure within the vacuum
chamber due to the high-pressure gas ejected from the static-pressure
bearings where possible.

[0966]A differential exhaust mechanism 145•24 is provided around the
leading end portion of the column 145•1, i.e. a charged beam
irradiating portion 145•2, so that the pressure of a charged beam
irradiation space 145•25 is kept at a sufficiently low level even
if the pressure within the vacuum chamber C is high. That is, A cyclic
member 145•26 of the differential exhaust mechanism 145•24
provided around the charged beam irradiating portion 145•2 is
positioned with respect to the housing 145•3 so that a very small
gap (several microns to several hundreds of microns) 145•27 is
formed between the lower face (face on the sample W side) of the cyclic
member 145•26, and a cyclic groove 145•28 is formed on the
lower face thereof. The cyclic groove 145•28 is connected to a
vacuum pump or the like (not shown) by an exhaust tube 145•29.
Thus, the very small gap 145•27 is evacuated through the cyclic
groove 145•28 and the exhaust port 145•29, and gas molecules
about to enter the space 145•25 surrounded by the cyclic member
145•26 from the vacuum chamber C is discharged. In this way, the
pressure within the charged beam irradiation space 145•25 can be
kept at a low level, and the charged beam can be applied without any
problems. This cyclic groove may have a double or triple structure
depending on the pressure within the charged beam irradiation space
145•25.

[0967]For the high-pressure gas supplied to the static-pressure bearing,
dry nitrogen is generally used. However, if possible, inert gas of higher
purity is preferably used. This is because if impurities such as water
and oil are contained in the gas, the impurity molecules are deposited on
the inner surface of the housing sectioning the vacuum chamber and the
surfaces of stage components to reduce the degree of vacuum, and
deposited on the sample surface to reduce the degree of vacuum in the
charged beam irradiation space. Furthermore, in the above description,
the sample W is not usually placed directly on the X table, but placed on
a sample table having functions of detachably holding the sample,
slightly changing the position with respect to the XY stage 145•4,
and so on, but existence/nonexistence of the sample table and its
structure are not related to the spirit of this embodiment, and are
therefore omitted for the sake of simplification.

[0968]In the charged beam apparatus described above, the stage mechanism
of the static-pressure bearing that is used in the atmosphere can be
almost directly used, thus making it possible to achieve a high-accuracy
XY stage equivalent to the atmosphere high-accuracy stage for use in the
light-exposure apparatus or the like for the XY stage for charged beam
apparatus at almost the same cost and in almost the same size.
Furthermore, the structure and layout of the static-pressure guide and
the actuator (linear motor) described above are only one example, and any
static-pressure guide and actuator capable of being used in the
atmosphere may be employed.

[0969]Next, examples of values of sizes of the cyclic member 145•26
of the differential exhaust mechanism and the cyclic groove formed
thereon are shown in FIG. 146. Furthermore, in this example, the cyclic
groove has a double structure of structures 146•1 and 146•2,
and these structures are isolated from each other in the radial
direction.

[0970]The flow rate of high-pressure gas supplied to the static-pressure
bearing is usually about 20 L/min (atmospheric pressure equivalent).
Provided that the vacuum chamber C is evacuated through a vacuum tube
having an inner diameter of 50 mm and a length of 2 m by a dry pump
having a pumping speed of 2000 L/min, the pressure within the vacuum
chamber is about 160 Pa (about 1.2 Torr). At this time, if the sizes of
the cyclic member 146•3 of the differential exhaust mechanism, the
cyclic groove and the like are set to those shown in FIG. 146, the
pressure within the charged beam irradiation space 141•1 can be
kept at 10-4 Pa(10-6 Torr).

[0971]Another embodiment of the XY stage is shown in FIG. 147. A dry pump
147•4 is connected through vacuum tubes 147•2 and 147•3
to the vacuum chamber C sectioned by a housing 147•1. Furthermore,
a turbo-molecular pump 147•9 being an ultrahigh vacuum pump is
connected to a cyclic groove 147•6 of a differential exhaust
mechanism 147•6 through a vacuum tube 147•8 connected to an
exhaust port 147•7.

[0972]Further, a turbo-molecular pump 147•13 is connected to the
inside of a column 147•10 through a vacuum tube 147•12
connected to an exhaust port 147•11. These turbo-molecular pumps
147•9 and 147•13 are connected to the dry vacuum pump
147•4 by vacuum tubes 147•14 and 147•15. In the figure,
one dry vacuum pump is used for the roughing vacuum pump of the
turbo-molecular pump and the pump for evacuation of the vacuum chamber,
but they may be evacuated with dry vacuum pumps of different systems
depending on the flow rate of high-pressure gas supplied to the
static-pressure bearing of the XY stage, the volume and the area of the
inner surface of the vacuum chamber, and the inner diameter and the
length of the vacuum tube.

[0973]High-purity inert gas (N2 gas, Ar gas, etc.) is supplied to the
static-pressure bearing of the XY stage through flexible tubes
147•16 and 147•16. The gas molecules ejected from the
static-pressure bearing diffuse into the vacuum chamber, and are
discharged by the dry vacuum pump 147•4 through exhaust ports
147•18, 147•19 and 147•20. Furthermore, these gas
molecules entering the differential exhaust mechanism and the charged
beam irradiation space are suctioned through the cyclic groove
147•6 or the leading end portion of the column 147•10,
discharged by the turbo-molecular pumps 147•9 and 147•13
through the exhaust ports 147•7 and 147•11, discharged from
the turbo-molecular pumps, and then discharged by the dry vacuum pump
147•4. In this way, the high-purity inert gas supplied to the
static-pressure bearing is collected in the dry vacuum pump and
discharged.

[0974]On the other hand, the exhaust port of the dry vacuum pump
147•4 is connected to a compressor 147•22 through a tube
147•21, and the exhaust port of the compressor 147•22 is
connected to the flexible tubes 147•16 and 147•17 through
tubes 147•23, 147•24 and 147•25 and regulators
147•26 and 147•27. Accordingly, the high-purity inert gas
discharged from the dry vacuum pump 147•4 is pressured again by the
compressor 147•22, adjusted to have an appropriate pressure by the
regulators 147•26 and 147•27, and then supplied again to the
static-pressure bearing of the XY stage.

[0975]Furthermore, since the gas supplied to the static-pressure bearing
should be purified as highly as possible, as described above, so that no
water and oil is contained in the gas, the turbo-molecular pump, the dry
pump and the compressor are required to have a structure such that no
water and oil enters the gas channel. Furthermore, it is also effective
to a cold trap, filter or the like (147•28) is provided at some
midpoint in the tube 147•23 on the discharge side of the compressor
to trap impurities such as water and oil entering the circulating gas, so
that they are not supplied to the static-pressure bearing.

[0976]Consequently, the high-purity inert gas can be circulated and
reused, thus making it possible to save the high-purity inert gas, and
the inert gas is not discharged into a room where this apparatus is
installed, thus making it possible to eliminate the possibility that
accidents such as suffocation by inert gas occur.

[0977]A high-purity inert gas supply system 147•29 is connected to a
circulation piping system, and plays a role to fill high-pressure inert
gas in the entire circulation system including the vacuum chamber C, the
vacuum tubes 147•8, 147•12, 147•14, 147•15,
147•2 and 147•3 and the pressure tubes 147•21,
147•23, 147•24, 147•25 and 147•30 when
circulation of the gas is started, and a role to supply an amount of gas
equivalent to a shortfall in case where the flow rate of gas drops for
some cause. Furthermore, by imparting to the dry vacuum pump 147•4
a function of compression to an atmospheric pressure or higher, one pump
can be made to serve as both the dry vacuum pump 147•4 and
compressor 147•22.

[0978]Further, for the ultrahigh vacuum pump for use in evacuation of the
column, a pump such as an ion pump or getter pump may be used instead of
the turbo-molecular pump. However, if such an entrapment vacuum pump is
used, the circulation piping system cannot be built in the area of the
pump. Furthermore, instead of the dry vacuum pump, a dry pump of a
different system such as diaphragm-type dry pump may be used as a matter
of course.

[0979]An optical system and a detector of the charged beam apparatus
according to this embodiment are schematically shown in FIG. 149. The
optical system is provided in a column, but the optical system and
detector are illustrative, and any optical system and detector may be
used as required. An optical system 149•1 of the charged beam
apparatus comprises a primary optical system 149•3 irradiating a
charged beam to a sample W placed on a stage 149•2, and a secondary
optical system 149•4 into which secondary electrons emitted from
the sample are introduced. The primary optical system 149•3
comprises an electron gun 149•5 emitting a charged beam, a lens
system 149•6 constituted by two-stage electrostatic lens converging
the charged beam emitted from the electron gun 149•5, a deflector
149•7, a Wien filter or E×B separator 149•8 deflecting
the charged beam so that its optical axis is perpendicular to the surface
of the object, and a lens system 149•9 constituted by a two-stage
lens, and these components are placed in order slantingly with respect to
the line of the optical axis of the charged beam perpendicular to the
surface of the sample (sample surface) with the electron gun 149•5
situated at the uppermost position as shown in FIG. 149. The E×B
deflector 149•8 comprises an electrode 149•10 and a magnet
149•11.

[0980]The secondary optical system 149•4 is an optical system into
which secondary electrons emitted from the sample W are introduced, and
comprises a lens system 149•12 constituted by a two-stage
electrostatic lens placed on the upper side of the E×B deflector
149•8 of the primary optical system. A detector 149•13
detects secondary electrons sent through the secondary optical system
149•4. The structures and functions of the components of the
optical system 149•1 and the detector 149•13 are the same as
those of the conventional system, and therefore detailed descriptions
thereof are not presented.

[0981]The charged beam emitted from the electron gun 149•5 is shaped
by a square aperture of the electron gun, downscaled by the two-stage
lens system 149•6, and has the optical axis adjusted by the
deflector 149•7 to form an image of a square of 1.925
mm×1.925 mm on the deflection central plane of the E×B
deflector. The E×B deflector 149•8 has a structure such that
an electric field is orthogonal to a magnetic field in the plane
perpendicular to the normal line of the sample, in which when a relation
in energy between the electric field and the magnetic field and the
electron meets a certain requirement, the electron is made to travel in a
straight line, and otherwise deflected in a predetermined direction
according to the mutual relation between the electric field and the
magnetic field and the electric field. In FIG. 149, the charged beam from
the electron gun is made to enter the sample W at a right angle, and
secondary electrons emitted from the sample are made to travel toward the
detector 149•13 in a straight line. The shaped beam deflected by
the E×B deflector is downscaled to 1/5 of the original scale by the
lens system 149•9 and projected on the sample W. Secondary
electrons having information of a pattern image, emitted from the sample
W, are enlarged by the lens systems 149•9 and 149•4 and form
a secondary electron image in the detector 149•13. This four-stage
enlargement lens is a deformation-free lens because the lens system
149•9 forms a symmetric tablet lens and the lens system
149•12 also forms a symmetric tablet lens.

[0982]According to this embodiment, the following effects can be
exhibited.

(1) Using a stage having a structure similar to that of a static-pressure
bearing-type stage that is generally used in the atmosphere
(static-pressure bearing support-type stage having no differential
exhaust mechanism), a sample on the stage can be stably processed with a
charged beam.(2) Influences on the degree of vacuum of a charged beam
irradiation area can be reduced to a minimum, and processing of the
sample with the charged beam can be stabilized.(3) An inspection
apparatus having a high performance in positioning of the stage and
having a stabilized degree of vacuum of the charged beam irradiation area
can be provided at a low cost.(4) A light-exposure apparatus having a
high performance in positioning of the stage and having a stabilized
degree of vacuum of the charged beam irradiation area can be provided at
a low cost.(5) A semiconductor is produced by an apparatus having a high
performance in positioning of the stage and having a stabilized degree of
vacuum of the charged beam irradiation area, whereby a fine semiconductor
circuit can be formed.

3-2) Other Embodiments of Electron Beam Apparatus

[0983]Further, another system with consideration of solving the problems
of this projection electron microscope type system is a system in which
using a plurality of primary electron beams, the plurality of electron
beams are scanned two-dimensionally (in X-Y direction) (raster-scanned)
to irradiate observation areas of the sample surface, and the secondary
electro-optical system employs a projection system.

[0984]This system has the advantage of the projection type system
described previously, and can solve the problems of this mapping system
such that (1) charge-up easily occurs on the sample surface because the
electron beam is collectively applied, and (2) the current of the
electron beam obtained with this system is limited (to about 1.6 μA),
which hinders an improvement in inspection speed, by scanning a plurality
of electron beams. That is, because the electron beam irradiation spot is
shifted, the charge easily escapes, resulting in a reduction in
charge-up. Furthermore, by increasing the number of the electron beams,
the current value can easily be increased. In the embodiment, if four
electron beams are used, total 2 μA of current is obtained with 500 nA
of current for one electron beam (diameter of electron beam: 10 μm).
The number of electron beams can easily be increased to about 16 and in
this case, it is possible to obtain 8 μA in principle. The scan of a
plurality of electron beams is not limited to the raster scan described
above, but may be any other from of scan such as a Lissajou's figure as
long as the amount of irradiation with a plurality of electron beams is
uniformly distributed over the irradiation area. Thus, the direction in
which the stage is scanned is not necessarily be perpendicular to the
direction of scan of the electron beam.

3-2-1) Electron Gun (Electron Beam Source)

[0985]A thermal electron beam source is used as an electron beam source
for use in this embodiment. The electron emission (emitter) material is
LaB6. Any other material can be used as long as it is a material having a
high melting point (low vapor pressure at high temperature) and having a
small work function. To obtain a plurality of electron beams, two methods
are used. One is a method in which one electron beam is drawn from one
emitter (one protrusion) and made to pass through a thin plate having a
plurality oh holes (aperture plate) to obtain a plurality of electron
beams, and the other is a method in which a plurality of protrusions are
formed on one emitter and a plurality of electron beams are draw directly
therefrom. Both the methods utilize the nature such that the electron
beam is easily emitted from the leading end of the protrusion. Other
types of electron beam sources, for example, a thermal electron beam
emission-type electron beam and a Schottky type can be used. Further, the
electron beam gun may emit a rectangular or linear beam, an aperture
shape may be used to create such a shape, the electron generation portion
(chip, filament or the like) of the electron gun may be formed into a
rectangular or linear shape.

[0986]Furthermore, the thermal electron beam source is a type of electron
beam source in which the electron emission material is heated to emit
electrons, and the thermal electric field emission electron beam source
is a type of electron beam source in which a high electric field is
applied to the electron emission material to emit electrons, and the
electron beam emission portion is heated to stabilize the emission of
electrons.

[0987]FIG. 150 A is a schematic diagram of electron beam apparatus of
another embodiment. On the other hand, FIG. 150 B is a schematic diagram
showing an aspect in which a sample is scanned with a plurality of
primary electron beams. An electron gun 150•1 capable of being
activated under space-charge limitation conditions forms a multi-beam
denoted by reference numeral 150•2 in FIG. 150 B. The multi-beam
150•2 is constituted by primary electron beams 150•3 that are
8 circular beams situated along a circumference.

[0988]A plurality of primary electron beams 150•3 generated at the
electron gun 150•1 are converged using lenses 150•5 and
150•6, and is adapted to enter a sample W at a right angle by an
E×B separator 150•9 comprised of an electrode 150•7 and
a magnet 150•8. The multi-beam 150•2 constituted by a
plurality of primary electron beams 150•3 converged on the sample W
by a primary optical system including the components 150•4,
150•5, 150•6, 150•9, a lens 150•10 and an
objective lens 150•11 is used for scanning on the sample W by a
two-stage deflector (not shown, included in the primary optical system)
provided on the downstream side of the lens 150•6.

[0989]The sample W is scanned in the direction of the x axis with the main
face of the objective lens 150•11 as the center of reflection. As
shown in FIG. 150 B, the primary electron beams 150•3 of the
multi-beam 150•2 are situated at a distance from each other along a
circumference, and are designed so that the distances between the
mutually adjacent primary electron beams 150•3 (measured at the
center of each primary electron beam) are the same when the primary
electron beams 150•3 are projected on the y axis orthogonal to the
x direction being a scan direction. At this time, the mutually adjacent
primary electron beams 150•3 may be separated from each other,
contact each other or partially overlap each other.

[0990]The overlapping pitch may be set to any value equal to or smaller
than 100 μm, preferably equal to or smaller than 50 μm, more
preferably equal to or smaller than 10 μm. By setting the overlapping
pitch to a value equal to or smaller than the pitch of the beam shape,
beams can be made to contact one another to form a linear shape.
Furthermore, beams originally formed into a rectangular or linear shape
may be used.

[0991]As shown in FIG. 150 B, the primary electron beams 150•3
constituting the multi-beam 150•2 are situated at a distance from
one another, whereby the limit value of the current density of the
individual primary electron beam, i.e. the marginal current density value
causing no charge on the sample W can be maintained at a level equivalent
to that when a single circular beam is used, thereby making it possible
to prevent a drop in S/N ratio. Furthermore, the primary electron beams
150•3 are situated at a distance from one another, and thus the
space charge effect is insignificant.

[0992]On the other hand, the multi-beam 150•2 can scan the sample W
over an entire filed of view 150•12 in a uniform density with one
scan. Consequently, image formation can be performed in high throughput,
thus making it possible to achieve a reduction in inspection time. In
FIG. 150 B, provided that reference numeral 150•2 denotes a multi
beam at the starting point of scanning, reference numeral 150•13
denotes a multi-beam at the endpoint of scanning.

[0993]The sample W is placed on a sample table (not shown). This table is
continuously moved along the y direction orthogonal to the scan direction
x at the time when the sample W is scanned in the x direction (e.g.
scanned in a width of 20 μm). In this way, raster scanning is
performed. A drive apparatus (not shown) for moving the table having the
sample placed thereon.

[0994]Secondary electrons generated from the sample W during scanning and
emitted in various directions are accelerated in the direction of the
optical axis by the objective lens 150•11 and as a result, the
secondary electrons emitted in various directions from various points are
each narrowly converged, and intervals of images are enlarged with lenses
150•10, 150•11, 150•14 and 150•15. A secondary
electron beam 150•16 formed via a secondary optical system
including the lenses 150•10, 150•11, 150•14 and
150•15 is projected on the light-receiving surface of a detector
150•17 to form an enlarged image of a field of view.

[0995]The detector 150•17 included in the optical system amplifies
the secondary electron beam with an MCP (micro-channel plate), converts
the amplified secondary electron beam into an optical signal with a
scintillator, and converts the optical signal into an electric signal
with a CCD detector. By the electric signal from the CCD, a
two-dimensional image of the sample W can be formed. Each primary
electron beam 150•3 should have a dimension of at least two pixels
of CCD pixels.

[0996]By operating the electron gun 150•1 under space-charge
limitation conditions, the shot noise of the primary electron beam
150•3 can be reduced in a order of one digit compared to operating
the electron gun under temperature limitation conditions. Thus, the shot
noise of the secondary electron signal can be reduced in a order of one
digit, thus making it possible to obtain a signal of a high S/N ratio.

[0997]According to the electron beam apparatus of this embodiment, the
limit value of the current density of the primary electron beam causing
no charge on the sample is maintained at a level equivalent to that when
a single circular beam is used, whereby a drop in S/N ratio is prevented,
and images are formed in high throughput, whereby inspection time can be
reduced.

[0998]In the device production process according to this embodiment, such
an electron beam apparatus is used to evaluate the wafer after each wafer
process is completed, whereby an improvement in yield can be achieved.

[0999]FIG. 151 shows the details of the electron beam apparatus according
to the embodiment of FIG. 150 A. Four electron beams 151•2
(151•3 to 151•6) emitted from an electron gun 151•1 are
shaped by an aperture diaphragm 1517, made to form an elliptic image of
10 μm×12 μm at the central face of deflection of a Wien
filter 151•10 by two-stage lenses 151•8 and 1519,
raster-scanned by a deflector 151•11, and made to form an image so
as to uniformly cover a rectangular area of 1 mm×0.25 mm as entire
four electron beams. A plurality of electron beams deflected by the
E×B 151•10 form a crossover with an NA diaphragm, and are
downscaled to 1/5 of the original scale by the lens 151•11 to cover
the sample with an area of 200μ×50 μm, and applied and
projected on the sample surface at a right angle (called Koehler
illumination). Four secondary electron beams 151•12 having
information of an pattern image (sample image F), emitted from the
sample, are enlarged by lenses 15•11, 151•13, 151•14,
and form an image on an MCP 151•15 as a rectangular image (enlarged
projection image F') synthesized with the four secondary electron beams
as a whole. The enlarged projection image F' with the four secondary
electron beams 151•12 are intensified by a factor of ten thousands
by the MCP 151•15, converted into light by a fluorescent screen,
changed to an electric signal synchronized with the speed of continuous
movement of the sample at a TDI-CCD 151•16, acquired as a
continuous image at an image display unit 151•17, and outputted to
a CRT or the like.

[1000]The electron beam irradiating portion should irradiate the sample
surface with an electron beam in an elliptic or rectangular form as
uniformly as possible and with reduced irradiation unevenness, and should
irradiate the irradiation area with the electron beam with a larger
current to improve the throughput. In the conventional system, the
electron beam irradiation unevenness is about ±10%, the image has
large contrast unevenness, and the electron beam irradiation current is
only about 500 nA in the irradiation area, resulting in a problem such
that high throughput cannot be obtained. Furthermore, this system has a
problem such that image formation tends to be hindered due to charge-up
because a wide image observation area is correctively irradiated with the
electron beam, compared with the scanning electron beam microscope (SEM)
system.

[1001]A method for irradiating a primary electron beam in this embodiment
is shown in FIG. 152. A primary electron beam 152•1 is constituted
by four electron beams 152•2 to 152•5, each beam has an
elliptic shape of 2 μm×2.4 μm, a rectangular area of 200
μm×12.5 μm is raster-scanned with one beam, and the beams are
added together in such a manner that they do not overlap one another to
irradiate a rectangular area of 200μ×50 μm as a whole. The
beam 151•2 reaches a spot 151•2' in finite time, then returns
to just below the spot 151•2 shifted by the diameter of the beam
spot (10 μm) with almost no time loss, moves again to just below the
spot 151•2' (toward a spot 151•3') in parallel to the line
151•2 to 151•2' in finite time in the same manner as
described previously, repeats this scan to scan 1/4 of a rectangular
irradiation area (200 μm×12.5 μm) shown by the dotted line in
the figure, then returns to the original spot 152•1, and repeats
this scan at a high speed.

[1002]The other electron beams 152•3 to 152•5 repeat scans at
the same speed as in the case of the electron beam 152•2 to scan
the rectangular irradiation area (200μ×50 μm) as a whole
uniformly and at a high speed.

[1003]The scan is not limited to the raster scan as long as the sample can
be uniformly irradiated. For example, the sample may be scanned in such a
manner as to draw a Lissajou's figure. Thus, the direction of movement of
the stage is not limited to the direction A shown in the figure. In other
words, the direction is not necessarily perpendicular to the scan
direction (lateral high-speed scan direction in the figure).

[1004]In this embodiment, the sample can be irradiated with electron beam
irradiation unevenness of about ±3%. The irradiation current is 250 nA
for one electron beam, and 1.0 μA of irradiation current can be
obtained with four electron beams as a whole on the sample surface (twice
as large as the irradiation current in the conventional system). By
increasing the number of electron beams, the current can be increased,
and thus high throughput can be obtained. Furthermore, the irradiation
spot is small compared to the conventional system (about 1/80 in area),
and the charge-up can be reduced to 1/20 of that of the conventional
system because the sample is moved.

[1005]Although not shown in the figure, this apparatus comprises units
required for irradiation with the electron beam and image formation such
as a limitation field diaphragm, a deflector (aligner) having 4 or more
poles for adjustment of the axis of the electron beam, an astigmatism
corrector (stigmater), and a plurality of quadrupolar lenses (quadrupole
lenses) for shaping a beam, in addition to lenses.

3-2-2) Structure of Electrode

[1006]FIG. 153 shows an electron beam apparatus having an electrode
structure for preventing insulation breakdown in an electro-optical
system using an electrostatic lens for irradiating the sample with an
electron beam.

[1007]Considerations have been made for using an electron beam apparatus
of high sensitivity and high resolution using an electron beam to inspect
the surface state of a fine sample such that a sufficient sensitivity and
resolution cannot be obtained by optical inspection.

[1008]In this electron beam apparatus, an electron beam is emitted by an
electron beam source, the emitted electron beam is accelerated and
converged with an electrostatic system such as an electrostatic lens, and
made to enter a sample as an inspection object. Then, a secondary
electron beam emitted from the sample with entrance of the electron beam
is detected, whereby a signal matching the detected secondary electron
beam is generated, and for example, data of the sample is formed with
this signal. The formed data is used to inspect the surface state of the
sample.

[1009]In the electro-optical system using an electrostatic lens such as an
electrostatic lens for use in the electron beam apparatus, electrodes
generating electric fields for accelerating and converging the electron
beam are provided in multiple stages along the optical axis of the
electron beam. A predetermined voltage is applied to each of these
electrodes and in this way, the electron beam is accelerated and
converged to a predetermined spot on the optical axis by the electric
field produced due to a difference in potential between electrodes.

[1010]In the conventional electron beam apparatus, part of the electron
beam emitted from the electron beam source may impinge upon the electrode
irrespective of the electric field in the electro-optical system using
the electrostatic lens. In this case, as the electron beam impinges upon
the electrode, a secondary electron beam is emitted from the electrode
itself. The amount of the secondary electron beam emitted from the
electrode varies depending on the material of the electrode, or the
material coated on the electrode. If the amount of the secondary electron
beam emitted from the electrode increases, the secondary electron beam is
accelerated by the electric field of the electrode and ionizes residual
gas in the apparatus, and the ions impinge upon the electrode, whereby a
secondary electron beam is further emitted from the electrode. Therefore,
if a large amount of secondary electron beam is emitted, a discharge
tends to occur between electrodes, thus raising the probability of
occurrence of insulation breakdown between electrodes.

[1011]For example, comparison of the probability of insulation breakdown
between the electrode coated with aluminum and the electrode coated with
gold showed that the probability of insulation breakdown between
electrodes was slightly higher in the case of the electrode coated with
aluminum. The work function of aluminum is 4.2 [eV] and the work function
of gold is 4.9 [eV]. Here, the work function means minimum energy
required for taking one electron beam in a metal into a vacuum (unit:
eV).

[1012]Furthermore, if the electrode is coated with gold, and the sample in
the electron beam apparatus is a semiconductor wafer, the gold may be
spattered and deposited on the surface of the semiconductor wafer as the
electron beam impinges upon the gold coating. If the gold is deposited on
the surface of the semiconductor, the gold is scattered in silicon
crystals in a subsequent heating step, resulting in degradation in
performance of a transistor. Thus, in this case, the electron beam
apparatus is not suitable for inspection of semiconductor wafers.

[1013]On the other hand, for example, in the electrostatic lens of the
electro-optical system using an electrostatic lens, an electrostatic lens
having a small focal distance is obtained by reducing the distance
between electrodes. If the focal distance is small, the electrostatic
lens has a reduced aberration coefficient and hence a low aberration, and
therefore the resolution of the electrostatic lens increases, resulting
in an improvement in resolution of an evaluation apparatus.

[1014]Also, by increasing a difference in potential to given to between
electrodes of the electrostatic lens, the focal distance of the
electrostatic lens can be reduced. Accordingly, as in the case of
reducing the distance between electrodes, the electrostatic lens has a
low aberration and a high resolution, and thus the resolution of the
electron beam apparatus is improved. Thus, if the distance between
electrodes is reduced and the difference in potential between electrodes
is increased, a reduction in aberration and an increase in resolution of
the electrostatic lens can be achieved in a synergistic manner. However,
if the distance between electrodes is reduced and the difference in
potential between electrodes is increased, a discharge tends to occur
between electrodes, thus increasing the probability of occurrence of
insulation breakdown between electrodes.

[1015]Hitherto, the insulation between electrodes has been retained by
inserting an insulating material between electrodes, and supporting the
electrodes with this insulating material. Furthermore, the insulation
performance of the insulating material has been improved by increasing
the shortest creepage distance (insulation surface length) of the
insulating material between electrodes. For example, by forming the
surface of the insulating material into a corrugation along the distance
between electrodes, the shortest creepage distance between electrodes can
has been increased.

[1016]Generally, however, the processing of the surface of the insulating
material is difficult compared to the processing of a metal, and thus
requires a high process cost. Furthermore, if the surface of the
insulating material is formed into a corrugation, the surface area of the
insulating material is increased, and therefore the amount of gas emitted
from the insulating material may increase in the case where a vacuum is
maintained in the electron beam apparatus. Accordingly, there have been
many cases where the degree of vacuum decreases, resulting in a drop in
withstand pressure between electrodes.

[1017]The embodiment of FIG. 153 has been proposed for solving these
problems, and the configuration and operation of a projection electron
microscope type evaluation apparatus and a device production process
using the apparatus where an electron beam apparatus capable of
preventing insulation breakdown between electrodes of an electrostatic
optical system is applied to the projection electron microscope type
evaluation apparatus having the electrostatic optical system, according
to this embodiment, will be described below.

[1018]In FIG. 153, for a projection electron microscope type evaluation
apparatus 153•1, an electron beam applied to a sample has
predetermined emitting surface, and a secondary electron beam emitted
from the sample with irradiation of the electron beam also has a
predetermined emitting surface. An electron beam having a two-dimensional
area, for example rectangular emitting surface is emitted from an
electron beam source 153•2, and enlarged by a predetermined
magnification by an electrostatic lens system 153•3. The enlarged
electron beam is made to enter an E×B deflector 153•4
slantingly from above, and deflected toward a semiconductor wafer
153•5 as a sample (solid line in FIG. 153) by a field in which an
electric field and a magnetic field of the E×B deflector
153•4 are orthogonal to each other.

[1019]The electron beam deflected toward the semiconductor wafer
153•5 by the E×B deflector 153•4 is retarded by an
electric field produced by a voltage applied to electrodes in an
electrostatic objective lens system 153•6, and made to form an
image on the semiconductor wafer 153•5 by the electrostatic
objective lens system 153•6.

[1020]Then, the secondary electron beam produced with irradiation of the
electron beam to the semiconductor wafer 153•5 is accelerated
toward a detector 153•7 (dotted line in FIG. 153) by the electric
field of the electrostatic objective lens system 153•6, and made to
enter the E×B deflector 153•4. The E×B deflector
153•4 forces the accelerated secondary electron beam toward an
electrostatic intermediate lens system 153•8, then causes the
electrostatic intermediate lens system 153•8 to make the secondary
electron beam enter the detector 153•7, whereby the secondary
electron beam is detected. The secondary electron beam detected by the
detector 153•7 is converted into data and sent to a display
apparatus 153•9, an image of the electron beam is displayed on the
display apparatus 153•9, and a pattern of the semiconductor wafer
153•5 is inspected.

[1021]The configurations of the electrostatic lens system 153•3, the
electrostatic objective lens system 153•6, the electrostatic
intermediate lens system 153•8 and the E×B deflector
153•4 in the projection type evaluation apparatus 153•1 will
now be described in detail. The electrostatic lens system 153•3 and
the electrostatic objective lens system 153•6 through which the
electron beam passes, and the electrostatic intermediate lens system
153•8 through which the secondary electron beam passes include a
plurality of electrodes for producing a predetermined electric field.
Furthermore, the surfaces of all the electrodes are coated with platinum.
Further, the surface of an electrode 153•10 of the E×B
deflector 153•4 is also coated with platinum.

[1022]Now, the probability of occurrence of insulation breakdown for each
metal coated on the electrode will be described with reference to FIG.
154. Furthermore, in the projection type evaluation apparatus, other
inspection conditions excluding the type of metal coated on the electrode
are the same.

[1023]First, comparison in probability of occurrence of insulation
breakdown between the case where aluminum is used as a metal coated on
the electrode and the case where gold is used as such a metal showed that
the probability of occurrence of insulation breakdown was slightly lower
in the electrode coated with gold. Thus, it was shown that gold had more
effective in prevention of insulation breakdown. Furthermore, comparison
in probability of occurrence of insulation breakdown between the case
where gold is used as a metal coated on the electrode and the case where
platinum is used as such a metal showed that the probability of
occurrence of insulation breakdown was lower in the electrode coated with
platinum.

[1024]Here, the work functions of the metals are 4.2 [eV] for aluminum,
4.9 [eV] for gold, and 5.3 [eV] for platinum. The work function of the
metal means minimum energy (unit: eV) required for taking one electron in
the metal into a vacuum. That is, as the value of the work function
increases, the electron beam becomes harder to be taken.

[1025]Accordingly, in the projection type evaluation apparatus
153•1, when the electron beam emitted from the electron beam source
153•2 impinges upon the electrode, the amount of secondary electron
beam emitted from the electrode decreases and thus the probability of
occurrence of insulation breakdown of the electrode is reduced as long as
the electrode is coated with a metal having a large work function value
(including an alloy having as a main material a metal having a large work
function value). Therefore, any material having a large work function is
somewhat acceptable. Specifically, if the work function of the metal
coated on the electrode is 5[eV], the probability of occurrence of
insulation breakdown of the electrode can be kept at a low level.

[1026]Furthermore, if, as in this embodiment, the sample to be inspected
is the semiconductor wafer 153•5, and the metal coated on the
electrode is gold, gold may be deposited on the pattern of the
semiconductor wafer 153•5 as the electron beam impinges upon the
gold. Accordingly, in this embodiment, if the metal coated on the
electrode is platinum, platinum is never deposited on the pattern of the
semiconductor wafer 153•5, and the device performance is never
compromised even if the platinum is deposited on the pattern. Further,
the probability of occurrence of insulation breakdown of the electrode
can be reduced, and thus platinum is more preferable.

[1027]One example of the shape and configuration of the electrode will now
be described with reference to FIGS. 155 and 156. In FIG. 155, an
electrode 155•1 is an electrode of an electrostatic lens included
in the electrostatic lens system 153•3, the electrostatic objective
lens system 153•6 and the electrostatic intermediate lens system
153•8.

[1028]The electrode 155•1 has a disk-like shape having at almost the
center a through-hole allowing the electron beam and secondary electron
beam to pass therethrough, and in the projection type evaluation
apparatus 153•1 of this embodiment, a predetermined voltage is
applied to the electrode 155•1 by a power supply apparatus (not
shown).

[1029]FIG. 156 is a partial sectional view of a surface portion of the
electrode 155•1. Furthermore, the surface of the electrode
153•10 of the E×B deflector 153•4 may have the same
configuration as that of the surface of the electrode 155•1. The
electrode 155•1 is made of silicon copper (silicon bronze) 156.1,
and titanium 156•2 is sputter-coated in the thickness of 50 nm on
the silicon copper 156•1 processed into a necessary size and shape,
and platinum 156•3 is sputter-coated in the thickness of 200 nm on
the titanium 156•2 to form the electrode 15511.

[1030]Now, the electron configuration for preventing insulation breakdown
between electrodes when the difference in potential between electrodes is
large in this embodiment will now be described in detail with reference
of FIGS. 157 and 158. Electrodes 157•1 and 157•2 of FIG. 157
are, for example, electrodes included in the electrostatic objective lens
system 153•6, and the electrodes are coated with platinum as
described above. Furthermore, predetermined voltages are applied to the
electrodes 157•1 and 157•2 by a power supply apparatus (not
shown). In this embodiment, a high voltage, for example a voltage of 15
kV is applied to the electrode 157•2 on the semiconductor wafer
153•5 side, and a voltage of 5 kV is applied to the electrode
157•1.

[1031]A through-hole 157•3 through which the electron beam and the
secondary electron beam pass is situated in the middle between the
electrodes 157•1 and 157•2, an electric field is formed in
the through-hole 157•3 by a difference in potential between the
electrodes 157•1 and 157•2. By this electric filed, the
electron beam is retarded and retarded, and is applied to the
semiconductor wafer 153•5. At this time the difference in potential
between the electrodes is large, and therefore the electrostatic
objective lens system 153•6 can have an electrostatic objective
lens having a small focal distance. Accordingly, the electrostatic
objective lens system 153•6 has a low aberration and a high
resolution.

[1032]An insulating spacer 157•4 is inserted between the electrodes
157•1 and 157•2, and the insulating spacer 157•4
approximately perpendicularly supports the electrodes 157•1 and
157•2. The shortest creepage distance between electrodes in the
insulating spacer 157•4 is proximately the same as the distance
between electrodes in the area of the supported electrode. That is, the
surface of the insulating spacer 157•4 between electrodes are not
corrugated or the like, but is almost a straight line.

[1033]The electrode 157•2 has a first electrode surface 157•5
with the shortest distance between electrodes, a second electrode surface
157•6 having a distance between electrodes longer than the first
electrode surface 157•5, and a step 157•7 in the direction of
the distance between these two electrodes between the first electrode
surface 157•5 and the second electrode surface 157•6 (FIG.
158). The insulating spacer 157•4 supports the electrode
157•2 with the second electrode surface 157•6.

[1034]Owing to this configuration of the electrode 157•2, the
shortest creepage distance of the insulating spacer 157•4 can be
made to be longer than the shortest distance between electrodes with the
shortest distance between electrodes being kept at a predetermined
distance and without processing the surface of the insulating spacer
157•4 into a corrugated shape in the direction of the distance
between electrodes. Furthermore, since a large electric field is not
applied to the surface of the insulating spacer 157•4, a structure
can be provided such that a creepage discharge is hard to occur.

[1035]Thus, the electrostatic objective lens system 135•6 can be
made to have an electrostatic objective lens having a small focal
distance, and have a low aberration and a high resolution, and the
performance of the insulating spacer 157•4 to provide insulation
between electrodes is not degraded, thus making it possible to prevent
insulation breakdown between electrodes. Furthermore, since the electrode
157•2 made of metal is processed so as to provide the step
157•7 thereon, the process cost is reduced compared with the case
where the insulating spacer 157•4 is processed. In addition, the
surface of the insulating spacer 157•4 in the direction of the
distance between electrodes has almost no irregularities, and the amount
of emitted gas from the insulating spacer 157•4 never increases.
Further, corner portions of an open end portion 157•8 of the
through-hole 157•3 of the electrode 157•1 and an open end
portion 157•9 of the through-hole 157•3 of the electrode
157•2 have curvatures, and therefore the electric field is never
concentrated on both the corner portions, thus making it possible to more
reliably prevent insulation breakdown between electrodes. Furthermore, a
corner portion of the step 157•7 of the electrode 157•2 on
the side between electrodes has a curvature, and therefore the electric
field is never concentrated on the corner portion, thus making it
possible to more reliably prevent insulation breakdown between
electrodes.

[1036]Furthermore, in this embodiment, the step 157•7 is provided on
the electrode 157•2, but the electrode 157•1 may also be
processed so as to provide a step in the direction of the electrode
157•2, or only the electrode 157•1 may be processed so as to
provide a step in the direction of the electrode 157•2 with the
electrode 157•2 having no step. Furthermore, the electrodes with
the insulating spacer 157•4 inserted therebetween has been
described in the electrostatic objective lens system 153•6, but if
there are electrodes having a large difference in potential in other
electrostatic lens system, the spacer 157•4 may be applied to the
electrostatic lens system to prevent insulation breakdown between
electrodes.

[1037]By using the embodiment described with FIGS. 153 to 158 in
inspection steps in the device production process already described, the
semiconductor wafer can be evaluated without causing insulation breakdown
to occur between electrodes of the electrostatic lens system.

3-3) Embodiment for Anti-Vibration Apparatus

[1038]This embodiment relates to an electron beam apparatus performing at
least any one of processing, production, observation and inspection of a
material by irradiating an electron beam to the target position of the
material, more particularly to an electron beam apparatus having reduced
undesired mechanical vibrations occurring in a mechanical structure
positioning the electron beam, an anti-vibration method thereof, and a
semiconductor production process comprising a step of performing at least
any one of processing, production, observation and inspection of a
semiconductor device using the electron beam apparatus.

[1039]Generally, means for observing a fine structure of a material using
an electron beam includes an inspection apparatus for inspecting defects
of a pattern formed on a wafer or the like, a scanning electron beam
microscope (SEM) and the like but in this case, the observation
resolution is μm to several tens of nm, and it is therefore required
to sufficiently remove external vibrations to make an observation.
Furthermore, in an apparatus for performing exposure system using an
electron beam, a vibration removal apparatus for sufficiently removing
external vibrations should be used to deflect an electron beam to
correctly irradiate the beam to the target position, and the rigidity
should be improved to reduce a drift caused by a mechanical resonance
resulting from the structure of a column portion to a minimum possible
level. To improve the rigidity of the structure, an improvement in
rigidity by reduction in size can hardly achieved because of the physical
limitation in size due to the electro-optical system, and thus an
improvement in rigidity is often achieved by thickening the wall of the
column portion, increasing the size and so on. However, the improvement
in rigidity by this method has many disadvantages including design
restrictions on the degree of freedom including an increase in weight of
apparatus, limitations on the shape and increase in size of a vibration
removal table, as well as economic aspects.

[1040]In view of the facts described above, this embodiment provides an
electron beam apparatus in which alleviation of design restrictions,
reduction in size and weight of apparatus, and improvement in economy are
achieved by appropriately attenuating undesired vibrations by a resonance
of a mechanical structure for positioning a beam so that the positioning
of the beam can be maintained with high accuracy without necessarily
improving the rigidity of the mechanical structure, and a semiconductor
production process capable of performing production, inspection,
processing, observation and the like using the apparatus in steps of
producing a semiconductor device.

[1041]FIG. 159 shows the configuration where this embodiment is applied to
an electron beam inspection apparatus inspecting defects of a
semiconductor wafer using en electron beam. An electron beam inspection
apparatus 159•1 shown in this figure is so called a projection type
apparatus, and has a mechanical structure of an A block and a B block
protruding upward slantingly from the A block. Primary electron beam
irradiating means for irradiating a primary electron beam is placed in
the B block, and a projection type optical system for mapping and
projecting a secondary electron beam, and imaging means for detecting the
intensity of the secondary electron beam are included in the A block. The
A block is coupled to a lowermost fixation base 159•2.

[1042]The primary electron beam irradiating means placed in the B block
comprises an electron beam source 159•3 constituted by a cathode
and an anode to emit and accelerate a primary electron beam, an oblong
opening 159•4 shaping the primary electron beam into an oblong, and
a quadrupole lens 159•5 reducing the primary electron beam and
making the primary electron beam form an image in a reduced size. An
E×B deflector 159•7 deflecting the reduced primary electron
beam so as to impinge upon a semiconductor wafer 159•6 at
approximately a right angle in a field in which an electric field E and a
magnetic filed B are orthogonal to each other, an aperture (NA) 159.8,
and an objective lens 159•9 making the primary electron beam
passing through the aperture form an image on the wafer 159•6 are
placed in the lower part of the A block.

[1043]Here, the primary electron beam reduced by the quadrupole lens
159•5 forms an image of, for example, 500 μm×250 μm on
the deflection main surface of the E×B deflector 159•7, and
also forms a crossover image of the electron beam source 159•3 on
the aperture 159•8, so that Keller illumination conditions are
satisfied. An image of, for example, 100 μm×50 μm is formed
on the wafer 159•6 by the objective lens 159•6.

[1044]The wafer 159•6 is placed in a sample chamber (not shown)
capable of being evacuated, and also placed on a stage 159•10
movable in the X-Y horizontal plane. Here, a relation between the A and B
blocks and an XYZ orthogonal coordinate system is shown in FIG. 160(a).
The wafer surface is situated in the X-Y horizontal plane, and the Z axis
is appropriately parallel to the optical axis of a projection optical
system. As the stage 159•10 moves in the X-Y horizontal plane with
the wafer 159•6 placed thereon, the inspection surface of the wafer
159•6 is sequentially scanned with the primary electron beam.
Furthermore, the stage 159•10 is placed on the fixation base
159•2.

[1045]The projection type optical system placed in the upper part of the A
block comprises an intermediate electrostatic lens 159•11, a
projection electrostatic lens 159•12, and a diaphragm 159•13
placed in the middle between these lenses. A secondary electron beam, a
reflection electron beam and a scattered electron beam emitted from the
wafer 159•6 with irradiation of the primary electron beam are
projected under a predetermined magnification (e.g. by factor of 200 to
300), and made to form an image on the lower face of a micro-channel
plate 159•14.

[1046]Imaging means placed at the top of the A block comprises the
micro-channel plate 159•14, a fluorescent screen 159•15, a
relay lens 159•16 and an imaging unit 159•17. The
micro-channel plate 159•14 has a large number of channels, and
further generates a large number of electron beams while the secondary
electron beam made to form an image by the electrostatic lenses
159•11 and 159•12 passes through the channels. That is, the
secondary electron beam is amplified. The fluorescent screen 159•15
emits fluorescence having an intensity appropriate to the intensity of
the secondary electron beam as the amplified secondary electron beam is
applied. That is, the intensity of the secondary electron beam is
converted into the intensity of light. The relay lens 159•16 is so
situated as to guide the fluorescence to the imaging unit 159•17.
The imaging unit 159•17 is constituted by a large number of imaging
devices for converting light guided by the relay lens 159•16 into
an electric signal. So called a TDI detector is preferably used to
improve the S/N ratio of a detection signal. Furthermore, not only the
secondary electron beam but also the back-scattered electron beam and the
reflection electron beam are generated with irradiation of the primary
electron beam, but these beams are collectively referred to as the
secondary electron beam here.

[1047]A column 160•1 comprised of the mechanical structure of the A
block and the B block coupled thereto usually has one or more
characteristic vibration modes. The resonance frequency and the resonance
direction of each characteristic vibration mode are determined according
to the shape, the weight distribution, the size, the layout of internal
machines and the like. For example, as shown in FIG. 160(b), the column
160•1 has at least a mode 1 of characteristic vibrations
160•2. In this mode 1, the column 160•1 drifts at a frequency
of 150 Hz approximately along the Y direction, for example. One example
of a transfer function of the column in this case is shown in FIG. 161.
In FIG. 161, the horizontal axis represents the frequency, and the
vertical axis represents the logarithm of vibration amplitude A. The
transfer function has a gain of a resonance magnification of 30 dB (about
a factor of 30) at a resonance frequency of 150 Hz. Thus, even if very
small vibrations are externally applied, frequency components at near 150
Hz are amplified by a factor of about 30 to vibrate the column if such
frequency components are included in the vibrations. As a result, a
detrimental event such as blurring of mapping is caused to occur.

[1048]To prevent such an event, the conventional technique takes
large-scale measures such as placing the entire column on a vibration
removal table to remove external vibrations, and/or reconsidering the
wall-thickness and structure of the column to reduce the resonance
magnification.

[1049]In this embodiment, to prevent the detrimental event, an actuator
160•4 applying pressure vibrations 160•3 to the column so as
to cancel out the vibrations 160•2 is placed in the base part of
the block A as shown in FIG. 160(c). This actuator 160•4 is
electrically connected to a vibration attenuating circuit 159•18.

[1050]The outlined configurations of the actuator 160•4 and the
vibration attenuating circuit 159•18 are shown in FIG. 162. As
shown in this figure, the actuator 160•4 has a piezoelectric
element 162•4 having a dielectric material 162•1 with a
piezoelectric effect held between electrodes 162•2 and 162•3,
and a support base 162•5 fixed on the fixation base 159•2 for
supporting the piezoelectric element from the electrode 162•3 side.
The piezoelectric element 162•4 is held between the A block of the
column 160•1 and the support base 162•5, the electrode
162•2 is fixed to the outer wall of the A block, and the electrode
162•3 is fixed to the support base 162•5. In this way, by the
reciprocating vibrations 160•2, the piezoelectric element
162•4 receives a positive pressure when the column 160•1
moves close to the element, and receives a negative pressure when the
column moves away from the element. The piezoelectric element 162•4
is situated at an effective position for inhibiting the vibrations
160•2 of the column 160•1. For example, it is preferably
situated so that the direction of the vibrations 160•2 is
orthogonal to the electrodes 162•2 and 162•3.

[1051]The vibration attenuating circuit 159•18 is comprised of a
variable inductance 162•6 and a resistance 162•7 connected in
series between both the electrodes 162•2 and 162•3 of the
piezoelectric element 162•4. Since the variable inductance
162•6 has an inductance L, the resistance 162•7 has a
resistance value of RD, and the piezoelectric element 162•4
has an electric capacitance of C, the piezoelectric element 162•4
and the vibration attenuating circuit 159•18 connected in series
are equivalent to a series resonance circuit denoted by reference numeral
162•8. The resonance frequency f0' of this series resonance
circuit is expressed by the following equation:

f0'=1/{2π(LC)1/2}.

In this embodiment, each parameter is set so that the resonance frequency
f0' of the series resonance circuit approximately equals the
resonance frequency f0 of the column 160•1. That is, the
inductance L of the variable inductance 162•6 is adjusted so that
the following equation holds for the electric capacitance C of the
piezoelectric element 162•4:

f0=1/2{2π(LC)1/2}.

[1052]Actually, the capacitance C of the piezoelectric element 162•4
is small in forming the resonance circuit according to the mechanical
resonance frequency, and hence a very large inductance L is often
required but in this case, a calculation amplifier or the like is used to
form equivalently large inductance, whereby the resonance circuit can be
achieved.

[1053]Furthermore, the value RD of the resistance 162•7 is
selected so that the Q value of a resonance frequency component of the
series resonance circuit approximately equals to the Q value of a
resonance component having a peak in the transfer function shown in FIG.
161. A series resonance circuit 162•8 created in this way has an
electric frequency characteristic denoted by reference numeral
161•1 of FIG. 161.

[1054]The electron beam inspection apparatus 159•1 shown in FIG. 159
is controlled/managed by a control unit 159•19. The control unit
159•19 can be constituted by a general personal computer or the
like as shown in FIG. 159. This computer a control unit main body
159•20 carrying out various kinds of control and calculation
operations according to a predetermined program, a CRT 159•21
displaying results of operations by the main body, and input unit
159•22 such as a keyboard, a mouse and the like for the operator to
input instructions. Of course, the control unit 159•19 may be
constituted by hardware dedicated to the electron beam inspection
apparatus, a workstation or the like.

[1055]The control unit main body 159•20 is constituted by a CPU, an
RAM, an ROM, a hard disk, various kinds of boards such as a video board
and the like (not shown). A secondary electron beam image storage area
159•23 for storing electric signals received from the imaging unit
159•17, i.e. digital image data of secondary electron beam images
of the wafer 159•6 is assigned on a memory of the RAM or hard disk.
Furthermore, a reference image storage unit 159•24 for storing
reference image data of the wafer having no defects in advance exists on
the hard disk. Further, in addition to a control program for controlling
the entire electron beam inspection apparatus, a defect detection program
159•25 is stored on the hard disk. This defect detection program
159•25 has a function of controlling the movement of the stage
159•10 in the XY plane, while carrying out various kinds of
calculation operations such as addition for digital image data received
from the imaging unit 159•17, and reconstituting a secondary
electron beam image on the storage area from data obtained as a result of
the operations. Further, this defect detection program 159•25 reads
secondary electron beam image data constituted on the storage area
159•23, and automatically detects defects of the wafer 159•6
according to a predetermined algorithm based on the image data.

[1056]The action of this embodiment will now be described. The primary
electron beam is emitted from the electron beam source 159•3, and
applied to the surface of the set wafer 159•6 through the oblong
opening 159•4, quadrupole lens 159•5, the E×B deflector
159•7 and the objective lens 159•9. As described above, an
inspection subject area of, for example, 100 μm×50 μm is
illuminated on the wafer 159•6, and the secondary electron beam is
emitted. This secondary electron beam is magnified and projected in the
lower face of the multi-channel plate 159•14 by the intermediate
electrostatic lens 159•11 and the projection electrostatic lens
159•12, and imaged by the imaging unit 159•17 to obtain a
secondary electron beam image of a projected area on the wafer
159•6. By driving the stage 159•10 to move the wafer
159•6 successively by each predetermined width in the X-Y
horizontal surface to carry out the above procedures, whereby an image of
the entire inspection surface can be obtained.

[1057]If an external force including a vibration component of the
resonance frequency f0 (150 Hz) is exerted on the column 160•1
while the enlarged secondary electron beam image is formed, the column
160•1 amplifies this vibration component with a resonance
magnification (30 dB) determined by the transfer function thereof and
characteristically vibrates. The vibrations 160•2 applies positive
and negative pressures to the piezoelectric element 162•4. The
piezoelectric element 162•4 temporarily converts vibration energy
of the column 160•1 into electric energy and outputs the same.
Since the inductance 162•6(L) and the resistance
162•7(RD) are connected in series to both the electrodes
162•2 and 162•3 to a resonance circuit, the capacitive
impedance of the piezoelectric element 162•4 and the dielectric
impedance L of the inductance 162•6 offset each other in the
resonance frequency f0, and the impedance of the resonance circuit is
only the resistance RD in effect. Thus, during resonance, electric
energy outputted from the piezoelectric element 162•4 is almost
fully consumed by the resistance 162•7(RD).

[1058]In this way, the piezoelectric element 162•4 produces a force
so as to offset an external force applied from the column 160•1 to
the piezoelectric element 162•4, and vibrations 160•2
produced by mechanical resonance can be offset to increase the resonance
magnification. The secondary electron beam is enlarged and mapped, and
therefore a drift in mapping by vibrations is further increased but in
this embodiment, blurring caused by this drift can be prevented before it
occurs.

[1059]As shown in FIG. 163, the resonance component of the transfer
function 161•1 of the column 160•1 (corresponding to FIG.
161) as a mechanical structure is offset by the resonance component of
the series resonance circuit 162•8 having electric frequency
characteristics 163•1, and thus the column 160•1 has a total
transfer function 163•2 having a low resonance magnification as a
whole.

[1060]As described above, when a satisfactory secondary electron beam
image free from blurring in mapping is obtained, then the electron beam
inspection apparatus 159•1 of this embodiment carries out
processing for inspecting defects of the wafer 159•6 from the
image. As defect inspection processing, so called a pattern matching
method or the like may be used. In this method, the reference image read
from the reference image storage unit 159•24 is matched with the
actually detected secondary electron beam image to calculate a distance
value representing similarity between both the images. If the distance
value is smaller than threshold value, it is determined that the
similarity is high to determine "no defects exit". On the other hand, if
the distance value is equal to or greater than the predetermined
threshold value, it is determined that the similarity is low to determine
that "defects exist". If it is determined that "defects exist", it may be
displayed for warning the operator. At this time, the secondary electron
beam image 159•26 may be displayed on the display unit of the CRT
159•21. Furthermore, the pattern matching method may be used for
each partial area of the secondary electron beam image.

[1061]There is a defect inspection method shown in FIGS. 164 (a) to (c)
other than the pattern matching method. In FIG. 164(a), an image
164•1 of a die detected first and an image 164•2 of another
die detected second are shown. If it is determined that still an image of
still another die detected third is identical or similar to the first
image 164•1, it is determined that an area 164•3 of the
second die image 164•2 has defects, and thus the defect area can be
detected.

[1062]In FIG. 164(b), an example of measurement of a line width of a
pattern formed on the wafer is shown. Reference numeral 164•6
denotes an intensity signal of an actual secondary electron beam when an
actual pattern 164•4 on a wafer is scanned in a direction
164•5, and a width 164•8 of an area in which this signal
continuously exceeds a threshold level 164•7 corrected and defined
in advance can be measured as the line width of the pattern 164•4.
If the line width measured in this way does not fall within a
predetermined range, it can be determined that the pattern has defects.

[1063]In FIG. 164(c), an example of measurement of a potential contrast of
a pattern formed on a wafer is shown. In the configuration shown in FIG.
159, an axisymmetric electrode 164•9 is provided above the wafer
159•6 and, for example, a potential of -10 V is given to the
electrode with respect to the potential of the wafer of 0 V. The
equipotential surface of -2 V at this time has a shape denoted by
reference numeral 14•10. Here, patterns 164•11 and
164•12 formed on the wafer have potentials of -4 V and 0 V,
respectively. In this case, a secondary electron beam emitted from the
pattern 164•11 has a upward speed equivalent to kinetic energy of 2
eV on the -2 V equipotential surface 164•10, and therefore passes
over the potential barrier 164•10, and escapes from the electrode
164•9 as shown in an orbit 164•13, and is detected by a
detector. On the other hand, a secondary electron beam emitted from the
pattern 164•12 cannot pass over the potential barrier of -2 V, and
is forced back to the wafer surface as shown in an orbit 164•14,
and therefore is not detected. Thus, the detection image of the pattern
164•11 is bright, and the detection image of the pattern
164•12 is dark. In this way, a potential contrast is obtained. If
the brightness and the potential of the detection image are corrected in
advance, the potential of the pattern can be measured from the detection
image. A defective area of the pattern can be evaluated from the
potential distribution.

[1064]As described above, by making measurements described above for the
satisfactory secondary electron beam image free from blurring in mapping
obtained from this embodiment, more accurate defect inspection can be
achieved.

[1065]If the electron beam inspection apparatus described as this
embodiment is used in wafer inspection steps in the device production
process, degradation in the detection image due to vibrations of the
mechanical structure can be prevented before it occurs, and therefore
accurate inspection can be carried out effectively, thus making it
possible to prevent defective products from being dispatched.

[1066]Furthermore, this embodiment is not limited to what has been
described above, but may be altered arbitrarily and suitably in the
spirit of the present invention. For example, not necessarily just one
mechanical resonance frequency and mode, but two or more mechanical
resonance frequencies and modes generally occur and in this case, they
can be coped with by placing a necessary number of actuators 160•4
at appropriate positions in the column. For example, if the mechanical
structure block A shown in FIG. 160(b) has not only vibrations
160•2 in the Y direction but also vibrations in the X direction, a
different actuator may be placed so as to offset the vibrations in the X
direction. Further, if the B block and the D block have independent
characteristic vibrations, actuators may be placed for these blocks.

[1067]The vibration actuating circuit 159•18 is not necessarily
equivalent to the series resonance circuit 162•8, but may be
matched with a circuit having a plurality of resonance frequencies as
electric frequency characteristics of the circuit if mechanical
characteristic vibrations have a plurality of resonance frequencies in
the same vibration direction.

[1068]The location in which the actuator is placed is not limited to the
column, but the actuator can also be applied to parts required to
correctly position the beam, for example the X-Y stage 159•10, or
optical parts of various kinds of optical instruments.

[1069]The semiconductor wafer 159•6 is used as an example of the
inspection subject sample of the electron beam inspection apparatus of
this embodiment, but the inspection subject sample is not limited
thereto, and any sample allowing defects to be detected with an electron
beam can be selected. For example, a mask or the like provided with a
pattern for light exposure for a wafer may be used as an inspection
object.

[1070]Further, this embodiment may be generally applied to the electron
beam irradiation apparatus irradiating a beam to a target position in a
material. In this case, this embodiment may be applied not only to the
apparatus carrying out inspection of the material but also extensively
applied to the apparatus carrying out any of processing, production and
observation thereof. Of course, the concept of the material refers not
only the wafer and the mask described above, but also any object capable
of being subjected to at least any one of inspection, processing,
production and observation with a beam. Similarly, the device
manufacturing method may be applied not only to inspection during the
step of producing a semiconductor device, but also to a process itself
for producing the semiconductor device with the beam.

[1071]Furthermore, the configuration shown in FIG. 159 is shown as that of
the electron beam inspection apparatus of this embodiment, but the
electro-optical system and the like may be altered arbitrarily and
suitably. For example, the electron beam irradiating means of the
electron beam inspection apparatus 159•1 has a form of making a
primary electron beam enter the surface of the wafer 159•6 at a
right angle from above, but the E×B deflector 159•7 may be
omitted to cause the primary electron beam enter the surface of the wafer
159•6 slantingly.

3-4) Embodiment for Wafer Holding

[1072]This embodiment relates to an electrostatic chuck adsorbing and
holding a wafer in an electrostatic manner in the electron beam
apparatus, a combination of a wafer and an electrostatic chuck,
particularly a combination of an electrostatic chuck and a wafer capable
of being used in an electron beam apparatus using a retarding-field
objective lens, and a device production process using an electron beam
apparatus comprising an electrostatic chuck and a wafer.

[1073]A well known electrostatic chuck adsorbing and fixing a wafer in an
electrostatic manner, an electrode layer to be placed on a substrate is
formed with a plurality of mutually insulated electrodes, and a power
supply apparatus applying voltages one after another from one electrode
to another electrode is provided. Furthermore, an electron beam apparatus
using a retarding-field objective lens is well known.

[1074]If the wafer under process is evaluated by the electron beam
apparatus using the retarding-field objective lens, it is necessary to
apply a negative high voltage to the wafer. In this case, if the negative
high voltage is rapidly applied, the device under process may be broken,
and therefore the voltage should be gradually applied.

[1075]On the other hand, for most wafers, insulation films such as
SiO2 or nitride films are deposited on the side and back faces of
the wafer, and therefore a problem arises such that when a zero potential
or low potential is to be given to the wafer, the voltage is not applied.
Further, there is a problem such that a wafer raised at the center toward
the electrostatic chuck side can be relatively easily adsorbed and fixed,
but a wafer recessed at the center toward the chuck side is held with its
edge portion chucked and its central portion not chucked with a unipolar
electrostatic chuck.

[1076]To solve the above problems, this embodiment provides an
electrostatic chuck capable of being used with the retarding-field
objective lens, having the side and back faces covered with insulation
films and capable of chucking the wafer recessed at the center toward the
chuck side, and a combination of a wafer and an electrostatic chuck, and
provides a device production process for evaluating a wafer under process
using this electrostatic chuck or combination of an electrostatic chuck
and wafer.

[1077]FIG. 165 is a plan view of an electrostatic chuck 1410 in this
embodiment, showing an electrode plate 165•1 after removal of a
wafer. FIG. 166 is a schematic sectional view in a vertical direction
along the M-M line of the electrostatic chuck of FIG. 165, showing a
state in which the wafer is placed and no voltage is applied. An
electrostatic chuck 165•2 has a laminated structure comprised of a
substrate 166•1, an electrode plate 166•2 and an insulation
layer 166•3 as shown in FIG. 166. The electrode plate 166•2
includes a first electrode 165•2 and a second electrode
165•3. The first electrode 165•2 and the second electrode
165•3 are separated from each other so that voltages can be
separately applied thereto, and they are made of thin film so that a
movement can be made at a high speed without producing an eddy current in
a magnetic field.

[1078]The first electrode 165•2 is comprised of the central part and
part of the periphery of the circular electrode plate 166•2 in the
plan view, and the second electrode 165•3 is comprised of the rest
horseshoe peripheral part of the electrode plate. The insulation layer
166•3 is placed above the electrode plate 166•2. The
insulation layer 166•3 is made of a sapphire substrate having a
thickness of 1 mm. Sapphire is made of single crystals of alumina and has
no pores unlike alumina ceramics, and therefore its insulation breakdown
voltage is high. For example, the sapphire substrate having a thickness
of 1 mm can sufficiently endure a difference in potential of 104 V
or greater.

[1079]A voltage is applied to a wafer 166•4 via a contact
166•5 having a knife-edged metal portion. As shown in FIG. 166, two
contacts 166•5 are made to contact the side face of the wafer
166•4. The reason why two contacts 166•5 are used is that
conduction may not be established if only one contact is used, and
occurrence of a force of pushing the wafer 166•4 toward one side
should be avoided. An insulation layer (not shown) is broken to establish
conduction, but because particles may be scattered when electrons are
discharged, the contact 166•5 is connected through a power supply
166•7 through a resistance 166•6 to prevent occurrence of a
large discharge. If this resistance 166•6 is too large, no
conduction hole is formed, and if the resistance 166•6 is too
small, a large discharge occurs to cause particles to be scattered, and
therefore the allowable value of the resistance is determined for each
insulation layer (not shown). This is because the thickness of the
insulation layer varies depending on the history of the wafer, and hence
the allowable value of the resistance should be determined for each
wafer.

[1080]FIG. 167(a) shows a time chart of voltage application. A voltage of
4 kV is applied to the first electrode at a time of t=0 as shown by the
line A. A voltage of 4 kV is applied to the second electrode as shown by
the line B at a time of t=t0 when the central part and peripheral
part of the wafer are both chucked. Control is performed so that a
voltage C of the wafer is gradually deepened (reduced) at a time of
t=t1, and reaches -4 kV at a time t=t2. The first and second
electrodes have voltages gradually reduced from a time of t=t1 to a
time of t=t2, and it reaches 0 V at a time t=t2.

[1081]At a time t=t3 when evaluation of the wafer adsorbed and held
by the chuck is completed, the voltage C of the wafer reaches 0 V, and
the wafer is taken to the outside.

[1082]If the electrostatic chuck adsorbs and holds the wafer with a
difference in potential of only 2 kV instead of 4 kV, voltages A' and B'
of 2 kV are applied to the first and second electrodes, respectively, as
shown by the dash-dot in FIG. 167. When a voltage of -4 kV is applied to
the wafer, voltages of -2 kV are applied to the first and second
electrodes, respectively. In this way, through voltage application,
application of a voltage to an insulation layer 2104 more than necessary
can be prevented, thus making it possible to prevent breakage of the
insulation layer.

[1083]FIG. 168 is a block diagram showing an electron beam apparatus
comprising the electrostatic chuck described above. An electron beam
emitted from an electron beam source 168•1 has an unnecessary beam
removed with an aperture of an anode 168•2 determining an aperture
(NA), reduced by a condenser lens 168•7 and an objective lens
168•13, made to form an image on the wafer 166•4 having a
voltage of -4 kV applied thereto, and made to scan the wafer 166•4
by deflectors 168•8 and 168•12. A secondary electron beam
emitted from the wafer 166•4 is collected by the objective lens
168•13, bent to the right at an angle of about 35° by an
E×B separator 168•12, and detected with a secondary electron
beam detector 168•10, and a SEM image on the wafer is obtained. In
the electron beam apparatus of FIG. 168, reference numerals 168•3
and 168•5 denote axis alignment devices, reference numeral
168•4 denotes an astigmatic correction device, reference numeral
168•6 denotes an aperture plate, reference numeral 168•11
denotes a shield, and reference numeral 168•14 denotes an
electrode. The electrostatic chuck described with FIGS. 166 and 167 is
placed below the wafer 166•4.

[1084]By using this embodiment in inspection steps in the device
production process, a semiconductor device having a fine pattern can be
inspected in high throughput, and 100% inspection can be performed, thus
making it possible to improve the yield of products and prevent defective
products being from dispatched.

[1085]Furthermore, how the voltage applied to the electrostatic chuck
increases and decreases is not limited to the way shown in FIG. 167 (a).
For example, the voltage may exponentially vary as shown in FIG. 167 (b).
It is only essential that the voltage should reach a predetermined
voltage within certain time.

[1086]The first to twelfth embodiments of the present invention have been
described in detail above but in any of the embodiments, the term
"predetermined voltage" means a voltage with which measurements such as
inspection are carried out.

[1087]Furthermore, the embodiments described previously use electron beams
as charged particle beams, but the charged particle beam is not limited
thereto, and a charged particle beam other than an electron beam, or a
non-charged particle beam such as a neutron beam having no charge, laser
light or an electromagnetic wave may be used.

[1088]Furthermore, when the charged particle beam apparatus according to
the present invention is activated, a target material is caused to float
and attracted to a high-pressure area by an adjacent interaction (charge
of particles near the surface), and therefore organic materials are
deposited on various electrodes for use in formation and deflection of
the charged particle beam. Organic materials gradually deposited as the
surface is charged badly affect mechanisms for forming and deflecting the
charged particle beam, and therefore these deposited organic materials
must be removed periodically. Thus, to periodically remove the deposited
organic materials, it is preferable that using an electrode near the area
having the organic materials deposited thereon, plasmas of hydrogen,
oxygen or fluorine and HF, H2O, CMFN and the like
containing these elements are produced under vacuum, and a plasma
potential in a space is kept at a potential (several kilovolts, e.g. 20 V
to 5 kV) allowing sputter to occur on the electrode surface to remove
only organic materials by oxidization, hydrogenation and fluorination.

3-5) Embodiment of E×B Separator

[1089]FIG. 169 shows an E×B separator 169•1 of this
embodiment. The E×B separator 169•1 is comprised of an
electrostatic deflector and an electromagnetic deflector, and is shown as
a sectional view on the x-y plane orthogonal to the optical axis (axis
perpendicular to the sheet face: z axis) in FIG. 169. The x axis
direction and the Y axis direction are also orthogonal to each other.

[1090]The electrostatic deflector comprises a pair of electrodes
(electrostatic deflection electrodes) 169•2 provided in a vacuum
chamber, and generates an electric field E in the X axis direction. The
electrostatic deflection electrodes 169•2 are attached to a vacuum
wall 169•4 of the vacuum chamber via an insulation spacer
169•3, and a distance D between these electrodes is set to a value
smaller than a length 2L in the y axis direction of the electrostatic
deflection electrode 169•2. By this setting, a range of uniform
electric field intensity formed around the Z axis can be made to be
relatively large but ideally, as long as the requirement of D<L is
met, the range of uniform electric field intensity can be increased.

[1091]That is, since the range extending from the edge of the electrode to
the position of D/2 does not have a uniform electric field intensity, an
area of almost uniform electric field intensity is an area of 2L-D at the
central part excluding the end area that does not have a uniform electric
field. Accordingly, in order that there exist an area of uniform electric
field intensity, the requirement of 2L>D should be met, and by setting
the requirement of L>D, the area of uniform electric field intensity
is further increased.

[1092]An electromagnetic deflector for generating a magnetic field M in
the Y axis direction is provided outside the vacuum wall 169•4. The
electromagnetic deflector comprises an electromagnetic coil 169•5
and an electromagnetic coil 169•6, and these coils generate
magnetic fields in x axis and Y axis directions, respectively.
Furthermore, a magnetic field M in the y axis direction can be generated
with the coil 169•6 alone, but a coil generating a magnetic field
in the x axis direction is provided for improving the orthogonality
between the electric field and the magnetic field M. That is, by
canceling out a magnetic component in the +x axis direction generated
with the coil 169•6 by a magnetic component in the -x axis
direction generated with the coil 169•6, the orthogonality between
the electric field and the magnetic field can be improved.

[1093]Since the coils 169•5 and 168•6 for generating magnetic
fields are provided outside the vacuum chamber, these coils are each
divided into two parts, and they are attached from both sides of the
vacuum wall 169•4, and fastened by screwing or the like in parts
169•7 to bond the parts together as one united body.

[1094]An outermost layer 169•8 of the E×B separator is
constituted as a yoke made of permalloy or ferrite. The outermost layer
169•8 may be divided into two parts, and the divided parts may be
attached to the outer face of the coil 169•6 from both sides, and
bonded together in the part 169•7 by screwing or the like as in the
case of the coils 169•5 and 169•6.

[1095]FIG. 170 shows a cross section orthogonal to the optical axis (z
axis) of an E×B separator 170•1 of this embodiment. The
E×B separator 170•1 of FIG. 170 is different from the
E×B separator of the embodiment shown in FIG. 169 in that six
electrostatic deflection electrodes 170•1 are provided. The
electrostatic deflection electrodes 170•1 are each supplied with a
voltage kcos θi (k is constant) proportional to cos
θi where an angle between a line extending from the center of
each electrode to the optical axis (z axis) and the direction of the
electric field (x axis direction) is θi (i=0, 1, 2, 3, 4, 5).
The θi is an arbitrary angle.

[1096]In the embodiment shown in FIG. 170, only the electric field in the
x axis direction can be produced, and thus the coils 169•5 and
169•6 for generating the magnetic field in the y axis direction are
provided to correct the orthogonality. According to this embodiment, the
area of uniform electric field intensity can be further increased
compared with the embodiment shown in FIG. 169.

[1097]In the E×B separators of the embodiments shown in FIGS. 169
and 170, the coil for generating a magnetic field is formed as a saddle
type, but a toroidal-type coil may be used.

[1098]In the E×B separator 169•1 of FIG. 169, since parallel
flat plate-type electrodes in which the size along the direction
perpendicular to the optical axis is larger than the distance between
electrodes are used as a pair of electrodes of the electrostatic
deflector to generate an electric field, the area in which a
uniform-intensity and parallel electric field is generated around the
optical axis is increased.

[1099]Further, in the E×B separators of FIGS. 169 and 170, since
saddle-type coils are used for the electromagnetic deflector, and the
angle between the optical axis and the coil is set to 2π/3 on one
side, no 3θ is generated and accordingly, the area in which a
uniform-intensity and parallel electric field is generated around the
optical axis is increased. Furthermore, since the magnetic field is
generated with the electromagnetic coil, a deflection current can be
superimposed on the coil and accordingly, a scanning function can be
provided.

[1100]The E×B separators of FIGS. 169 and 170 are each constituted
as a combination of an electrostatic deflector and an electromagnetic
deflector, and therefore by calculating the aberration of the
electrostatic deflector and the lens system, calculating the aberration
of the electromagnetic deflector and the lens system aside therefrom, and
summing the aberrations, the aberration of the optical system can be
obtained.

3-6) Embodiment of Production Line

[1101]FIG. 171 shows an example of a production line using the apparatus
of the present invention. Information such as the lot number of a wafer
to be inspected by an inspection apparatus 171•1 and the history of
production apparatus involved in production can be read from a memory
provided in an SMIF or FOUP 171•2, or the lot number can be
recognized by reading ID number of the SMIF, FOUP or wafer cassette.
During transportation of the wafer, the amount of water is controlled to
prevent oxidization and the like of metal wiring.

[1102]The defect inspection apparatus 171•1 can be connected a
network system of the production line, and information such as the lot
number of the wafer as an inspection subject and the results of
inspection can be sent to a production line control computer 171•4
controlling the production line, each production apparatus 171•5
and other inspection apparatus via the network system 171•3. The
production apparatuses include lithography-related apparatuses, for
example, a light-exposure apparatus, a coater, a cure apparatus and a
developer, or film formation apparatuses such as an etching apparatus, a
spattering apparatus and a CVD apparatus, a CMP apparatus, various kinds
of measurement apparatuses, other inspection apparatuses and a review
apparatus.

3-7) Embodiment Using Other Electrons

[1103]The essential object of the present invention is to irradiate an
electron beam to a sample such as a substrate provided with a wiring
pattern having a line width of 100 nm or smaller, and detect electrons
obtaining information of the surface of the substrate, acquiring an image
of the surface of the substrate from the detected electrons to inspect
the sample surface. Particularly, the present invention proposes an
inspection process and apparatus in which when the electron beam is
applied to the sample, an electron beam having an area including a
certain imaging area is applied, electrons emitted from the imaging area
on the substrate are made to form an image using a CCD, CCD-TDI or the
like to acquire an image of the imaging area, and the obtained image is
inspected with cell inspection and die comparison inspection combined as
appropriate depending on the pattern of dies, whereby throughput much
higher compared to the SEM process is achieved. That is, the inspection
process and inspection apparatus using an electron beam in the present
invention solves both problems such that in an optical inspection
apparatus, defects of a pattern having a line width of 100 nm or smaller
cannot be sufficiently inspected due to a low resolution, and that in a
SEM inspection apparatus, inspection requires too much time to meet the
requirement of high throughput, thus making it possible to inspect a
wiring pattern having a line width of 100 nm or smaller in a sufficient
resolution and high throughput.

[1104]In inspection of the sample, it is desirable in terms of the
resolution that the electron beam is made to impinge upon the substrate,
and electrons emitted from the substrate are detected to obtain an image
of the surface of the substrate. Thus, the examples of the present
invention have been described mainly focusing on secondary electrons,
reflection electrons and back-scattered electrons emitted from the
substrate. However, electrons to be detected may be any electrons
obtaining information of the surface of the substrate, and may be, for
example, mirror electrons (reflection electrons in a brad sense)
reflected near the substrate instead of directly impinging upon the
substrate by forming an inverse electric field near the substrate,
transmission electrons passing through the substrate, or the like. In
particular, use of mirror electrons has an advantage that the effect of
charge-up is very small because electrons do not directly impinge upon
the sample.

[1105]In the case where mirror electrons are used, a negative potential
lower than an accelerating voltage is applied to the sample to form an
inverse electric field near the sample. This negative potential is
preferably set to a value such that most electron beams are forced back
near the surface of the substrate. Specifically, it may be set at a
potential that is 0.5 to 1.0 V or more lower than the acceleration
voltage. For example, in the present invention, the voltage to be applied
to the sample is preferably set to -4.000 kV to -4.050 kV if the
accelerating voltage is -4 kV. It is more preferably set to -4.0005 kV to
-4.020 kV, further more preferably -4.0005 kV to -4.010 kV.

[1106]Furthermore, in the case where transmission electrons are used, the
voltage to be applied to the sample is set to 0 to -4 kV, preferably 0 to
-3.9 kV, more preferably 0 to -3.5 kV if the accelerating voltage is set
to -4 kV.

[1107]In addition, an X ray may be used instead of the electron beam. The
secondary system and die comparison can be sufficiently applied.

[1108]Irrespective of which of mirror electrons or transmission electrons
are used, the electron gun, the primary optical system, the deflector for
separating the primary electron beam from the detection electron beam,
the detector using the CCD or CCD-TDI, the image processing apparatus,
the calculation device for die comparison, and the like already described
are used. An electron beam having a certain area such as an ellipse is
used, but a finely focused electron beam for use in a SEM type may be
used as a matter of course. One electron beam or two or more electron
beams may be used as a matter of course. For the deflector for separating
the primary electron beam from the detection electron beam, a Wien filter
forming both electric and magnetic fields may be used, or a deflector
forming only the magnetic field may be used. For the detector, a CCD or
CCD-TDI capable of forming an imaging area on the detector to carry out
speedy inspection is used, but if a SEM-type electron gun is used, a
semiconductor detector or the like corresponding to such a type of
electron gun is used as a matter of course. If an image of the surface of
the substrate is acquired, and comparison inspection of dies is carried
out, cell inspection to be applied to a cyclic pattern and comparison
inspection of dies to be applied a random pattern are used as
appropriated depending on the pattern of dies. Of course, only comparison
inspection of dies may be carried out and in the case of comparison
inspection of dies, a dies on the same substrate may be compared, or dies
on different substrates may be compared, or the die may be compared with
CAD data. Suitable of them may be arbitrarily used. Further, the
substrate is aligned before inspection. A positional deviation of the
substrate is measured, and a deviation in rotation angle is corrected. At
this time, a focus map may be created to carry out inspection while
correcting the position of the substrate on the plane and a deviation in
focus in consideration of the map during inspection.

[1109]Furthermore, when the apparatus of the present invention is used in
production steps, it is desirable that information of the wafer as an
inspection object is acquired from a computer connected to the network
system for controlling the production system, and inspection results are
sent to incorporate the results in production conditions of apparatuses
in the production line.

3-8) Embodiment Using Secondary Electrons and Reflection Electrons

[1110]This embodiment relates to a projection type electron beam apparatus
of high resolution and high throughput capable of irradiating an
inspection object with a plane beam and switching between secondary
electrons and reflection electrons depending on the inspection object. In
this way, the type of irradiating an electron beam not to one spot on a
sample but to a field of view extending at least two-dimensionally to
form an image of the field of view is called a "projection electron
microscope type". This projection-type electron beam apparatus is a
high-resolution and high-throughput apparatus capable of avoiding a space
charge effect, having a high signal-to-noise ratio and having an enhanced
image processing by parallel processing.

[1111]The implementation of the projection-type electron beam apparatus of
this embodiment as a defect inspection apparatus will be described in
detail below with reference to FIGS. 172 to 181. Furthermore, in these
figures, like reference numerals or reference symbols denote identical or
corresponding components.

[1112]In FIGS. 172 (A) and (B), an electron gun EG of a defect inspection
apparatus EBI has a thermal electron beam emitting LaB6 cathode 1
capable of operating at a large current, and primary electrons emitted in
a first direction from the electron gun EG pass through a primary optical
system including several stages of quadrupole lenses 2 to have the beam
shape adjusted, and then pass through a Wien filter 172•1. By the
Wien filter 172•1, the traveling direction of the primary electrons
is changed to a second direction so that they enter a wafer W as an
inspection object. The primary electrons exiting from the Wien filter
172•1 and traveling in the second direction has the beam diameter
limited by an NA aperture plate 172•2, pass through an objective
lens 172•3, and are applied to the wafer W. The objective lens
172•3 is a high-accuracy electrostatic lens.

[1113]In this way, in the primary optical system, an electron gun of high
luminance made of LaB6 is used as the electron gun EG, thus making
it possible to obtain a primary beam having low energy, a large current
and a large area compared to the conventional scanning defect inspection
apparatus.

[1114]Since the wafer W is irradiated with a plane beam with the
cross-section formed into a rectangular shape of, for example, 200
μm×50 μm by the primary optical system, a small area on the
wafer W having a predetermined area can be irradiated. To irradiate the
wafer W with this plane beam, the wafer W is placed on a high-accuracy XY
stage (not shown) coping with a 300 mm wafer, for example, and the XY
stage is two-dimensionally moved with the plane beam fixed. Furthermore,
because it is not necessary to focus the primary electrons on a beam
spot, the plane beam has a low current density, and thus the damage of
the wafer W is reduced. For example, the current density of the beam spot
is 103 A/cm2 in the conventional beam scanning defect
inspection apparatus, while the current density of the plane beam is only
0.1 A/cm2 to 0.01 A/cm2 in the defect inspection apparatus EBI
shown in the figure. On the other hand, the dose is 1×10-5
C/cm2 in the conventional beam scanning type, while the dose is
1×10-4 C/cm2 to 3×10-5 C/cm2 in this
type, and this type of apparatus has a higher sensitivity.

[1115]Secondary electrons and reflection electrons are emitted from an
area of the wafer irradiated with the plane beam-shaped primary
electrons. Reflection electrodes will be described later and for
explanation of detection of secondary electrons, first, the secondary
electrons emitted from the wafer W, destined to travel in a direction
opposite to the second direction, are enlarged by the objective lens
172•3, pass through the NA aperture plate 172•2 and the Wien
filter 172•1, are enlarged again by an intermediate lens
172•4, further enlarged by a projection lens 172•5, and
enters a secondary electron detection system D. In a secondary optical
system guiding secondary electrons, the objective lens 172•3, the
intermediate lens 172•4 and the projection lens 172•5 are all
high-accuracy lenses, and the secondary optical system is configured to
have a variable magnification. Because the primary electrons are made to
enter the wafer W at almost a right angle, and the secondary electrons
are taken out at almost a right angle, shading caused by irregularities
on the surface of the wafer does not occur.

[1116]The secondary electron detection system D receiving secondary
electrons from the projection lens 172•5 comprises a micro-channel
plate 172•6 multiplying entering secondary electrons, a fluorescent
screen 192•7 converting the electrons exiting the micro-channel
plate 172•6 into light, and a sensor unit 172•8 converting
the light emitting from the fluorescent screen 172•6 into an
electric signal. The sensor unit 172•8 has a high-sensitivity line
sensor 172•9 constituted by a large number of two-dimensionally
arranged solid imaging devices, and fluorescence emitted from the
fluorescent screen 172•7 is converted into an electric signal by
the line sensor 172•9, sent to an image processing unit
172•10, and processed in parallel, in multiple stages and at a high
speed.

[1117]While the wafer W is moved to irradiate and scan individual areas on
the wafer W with a plane beam one after another, the image processing
unit 172•10 accumulates data about XY coordinates and images of
areas including defects, and creates an inspection result file including
coordinates and images of all areas of an inspection object including
defects for one wafer. In this way, inspection results can be
collectively managed. When this inspection result file is read out, a
defect distribution and a defect detail list of the wafer is displayed on
a display of the image processing unit 172•10.

[1118]In fact, of various components of the defect inspection apparatus
EBI, the sensor unit 172•8 is placed in the atmosphere, but other
components are placed in a column kept under vacuum and therefore, in
this embodiment, a light guide is provided on an appropriate wall surface
of the column, so that light exiting from the fluorescent screen
172•7 is taken out into the atmosphere through the light guide, and
passed to the line sensor 172•9.

[1119]FIG. 173 shows a specific example of the configuration of the
secondary electron detection system D in the defect inspection apparatus
EBI of FIG. 172. A secondary electron image or reflection electron image
173•1 is formed on the entrance surface of the micro-channel plate
172•6 by the projection lens 172•5. The micro-channel plate
172•6 has, for example, a resolution of 16 μm, a gain of
103 to 104 and 2100×520, and multiplies electrons
according to the formed electron image 173•1 to irradiate the
fluorescent screen 172•7. Consequently, fluorescence is emitted
from an area of the fluorescent screen 172•7 irradiated with
electrons, and the emitted fluorescence is discharged into the atmosphere
through the light guide 173•2 of low deformation (e.g. 0.4%). The
emitted fluorescence is made to enter the line sensor 172•9 through
an optical relay lens 173•3. For example, the optical relay lens
173•3 has a magnification of 1/2, a transmittance of 2.3% and a
deformation of 0.4%, and the line sensor 172•9 has a pixel number
of 2048×512. The optical relay lens 173•3 forms an optical
image 173•4 matching the electron image 173•1 on the entrance
surface of the line sensor 172•9. An FOP (fiber optic plate) may be
used instead of the light guide 173•2 and the relay lens
173•3 and in this case, the magnification is 1×.

[1120]The defect inspection apparatus EBI shown in FIG. 172 can be
operated in one of a positive charge mode and a negative charge mode, in
the case of secondary electrons, by adjusting an accelerating voltage of
the electron gun EG and a wafer electrode applied to the wafer W and
using the electron detection system D. Further, by adjusting the
accelerating voltage of the electron gun EG, the wafer voltage applied to
the wafer W and objective lens conditions, the defect inspection
apparatus EBI can be operated in a reflection electron imaging mode to
detect reflection electrodes of high energy emitted from the wafer W with
irradiation of primary electrons. Since reflection electrodes have energy
equal to energy of the primary electrons entering a sample such as the
wafer W, and thus have energy higher than that of secondary electrons,
the reflection electrodes are hard to be influenced by a potential such
as charge of the surface of the sample. For the electron detection
system, an electron impact detector such as an electron impact CCD or
electron impact TDI outputting an electric signal matching the intensity
of secondary electrons or reflection electrons may be used. In this case,
the micro-channel plate 172•6, the fluorescent screen 172•7
and the relay lens 173•3 (or FOP) are not used, but the electron
impact detector is placed at an image formation position and used. This
configuration enables the defect inspection apparatus EBI to operate in a
mode suitable for an inspection object. For example, the negative charge
mode or reflection electron imaging mode may be used for detecting
defects of metal wiring, defects of gate contact (GC) wiring or defects
of a resist pattern, and the reflection electron imaging mode may be used
to detect poor conduction of a via, or residues on the bottom of the via
after etching.

[1121]FIG. 174 (A) illustrates requirements for operating the defect
inspection apparatus EBI of FIG. 1 in the three modes described above.
The accelerating voltage of the electron gun EG is VA, the wafer
voltage applied to the wafer W is VW, the irradiation energy of
primary electrons when the wafer W is irradiated is EIN, and the
signal energy of secondary electrons entering the electron detection
system D is EOUT. The electron gun EG is configured so that the
accelerating voltage VA is variable, and the variable wafer voltage
VW is applied to the wafer W from an appropriate power supply (not
shown). Then, if the accelerating voltage VA and the wafer voltage
VW are adjusted, and the electron detection system D is used, the
defect inspection apparatus EBI can operate in the positive charge mode
in the range of the secondary electron yield greater than 1, and can
operate in the negative mode in the range of the secondary electron yield
smaller than 1 as shown in FIG. 174(B). Furthermore, by adjusting the
accelerating voltage VA, the wafer voltage VW and the objective
lens conditions, the defect inspection apparatus EBI can operate in the
reflection electron imaging mode using a difference in energy between
secondary electrons and reflection electrons. Furthermore, in FIG.
174(B), in fact, the value of electron irradiation energy EIN at the
boundary between the positive charge area and the negative charge area
varies depending on the sample.

[1122]One example of values of VA, VW, EIN and EOUT
for operating the defect inspection apparatus EBI in the reflection
electron imaging mode, the negative charge mode and the positive charge
mode is described below.

Values in reflection electron imaging mode:

VA=-4.0 kV;

VW=-2.5 kV;

EIN=1.5 keV; and

EOUT=4 keV.

Values in negative charge mode:

VA=-7.0 kV;

VW=-4.0 kV;

EIN=3.0 keV; and

EOUT=4 keV+α(α=energy width of secondary electrons).

Values in positive charge mode:

VA=-4.5 kV;

VW=-4.0 kV;

EIN=0.5 keV; and

EOUT=4 keV+α(α=energy width of secondary electrons).

[1123]In fact, the detection amounts of secondary electrons and reflection
electrons vary depending on the surface composition of the inspection
subject area on the wafer W, the pattern shape and the surface potential.
That is, the yield of secondary electrons and the amount of reflection
electrons vary depending on the surface composition of the inspection
subject on the wafer W, and the yield of secondary electrons and the
amount of reflection electrons are larger at pointed sites and corners
than in plane areas. Furthermore, if the surface potential of the
inspection subject on the wafer W is high, the amount of emitted
secondary electrons decreases. In this way, the intensities of electric
signals obtained from secondary electrons and reflection electrons
detected by the detection system D vary depending on the material, the
pattern shape and the surface potential.

[1124]FIG. 175 shows the shape of the cross-section of each electrode of
the electrostatic lens for use in the electro-optical system of the
defect inspection apparatus EBI shown in FIG. 172. As shown in FIG. 175,
the distance between the wafer W and the micro-channel plate 172•6
is, for example, 800 mm, and the objective lens 172•3, the
intermediate lens 172•4 and the projection lens 172•5 are
electrostatic lenses each having a plurality of electrodes having
specific shapes. Now, if a voltage of -4 kV is applied to the wafer W, a
voltage of +20 kV is applied to an electrode of the objective lens
172•3, which is closest to the wafer W, and a voltage of -1476 V is
applied to other electrodes. At the same time, a voltage of -2450 V is
applied to the intermediate lens 172•4, and a voltage of -4120 V is
applied to the projection lens 172•5. As a result, the
magnification obtained with the secondary optical system is 2.4 with the
objective lens 172•5, 2.8 with the intermediate lens 172•4,
and 37 with the projection lens 172•5, resulting in total 260.
Furthermore, in FIG. 175, reference numerals 175•1 and 175•2
denote field apertures for limiting the beam diameter, and reference
numeral 175•3 denotes an deflector.

[1125]FIG. 176(A) schematically shows the configuration of a
multi-beam/multi-pixel-type defect inspection apparatus EBI that is
another embodiment of a projection type electron beam apparatus. An
electron gun EGm in this defect inspection apparatus is a multi-beam-type
electron gun having a LaB6 cathode and capable of emitting a
plurality of primary electron beams 176•1. The primary electron
beams 176•1 have beam diameters adjusted by an aperture plate
176•2 provided with pores at positions corresponding to the primary
electron beams, then have beam positions adjusted by two-stage
axisymmetric lenses 176•3 and 176•4, travel in a first
direction, pass through the Wien filter 172•1, change the traveling
direction from the first direction to a second direction, and travel so
as to enter the wafer W. Thereafter, the primary electron beams
176•1 pass through the NA aperture plate 172•2 and the
objective lens 172•3, and are applied to predetermined areas of the
wafer W.

[1126]Secondary electrodes and reflection electrodes 176•5 emitted
from the wafer W with irradiation of the primary electron beams
176•1 travel in a direction opposite to the second direction to
pass through the objective lens 172•3, the NA aperture plate
172•2, the Wien filter 172•1, the intermediate lens
172•4 and the projection lens 172•5, enters the detection
system D, and is converted into an electric signal by the sensor unit
172•8 in the same manner as described with FIG. 172(A).

[1127]A deflector 176•6 for deflecting the primary electron beams
176•1 is placed between the axisymmetric lens 176•4 situated
on the downstream side when seen from the electron gun EGm and the Wien
filter 172•1. To scan a certain area R on the wafer W with the
primary electron beams 176•1, the primary electron beams
176•1 are deflected in the x axis direction perpendicular to the Y
axis at a time by the deflector 176•6 while the wafer W is moved in
the Y axis as shown in FIG. 176 (B). In this way, the area R is
raster-scanned with the primary electron beams 176•1.

[1128]FIG. 177(A) shows the outlined configuration of a
multi-beam/mono-pixel-type defect inspection apparatus EBI that is still
another embodiment of a projection type electron beam apparatus. In this
figure, the electron gun EGm can emit a plurality of primary electron
beams 176•1, and the emitted primary electron beams 176•1 are
guided by the aperture plate 176•2, the axisymmetric lenses
176•3 and 176•4, the deflector 176•6, the Wien filter
172•1 and the objective lens 172•3 so as to travel in the
first direction, and are applied to the wafer W in the same manner as
described with FIG. 176(A).

[1129]Secondary electrons or reflection electrons 176•5 emitted from
the wafer W with irradiation of the primary electron beams 176•1
pass through the objective lens 172•3, then have the traveling
direction changed by a predetermined angle by the Wien filter
172•1, then pass through the intermediate lens 172•4 and the
projection lens 172•5, and enter a multi-detection system D'. The
multi-detection system D' in this figure is a secondary electron
detection system, and comprises a multi-aperture plate 177•1
provided with pores identical in number to n pores formed in the aperture
electrode 176•2, n detectors 177•2 provided in correspondence
with the pores of the multi-aperture plate 177•1 so that secondary
electrons passing through the n pores of the aperture plate 177•1
are captured and converted into electric signals indicating the intensity
of the secondary electrons, n amplifiers 177•3 amplifying the
electric signals outputted from the detectors 177•2, and an image
processing unit 172•10' converting into digital signals the
electric signals amplified by the amplifiers 177•3, and performing
storage, display, comparison and the like of image signals of an scan
subject area R on the wafer W.

[1130]In the defect inspection apparatus EBI shown in FIG. 177(A), the
area is scanned with the primary electron beams 176•1 in a manner
as shown in FIG. 177(B). That is, as shown in FIG. 177 (B), the area R is
divided in the Y axis direction by the number of primary electron beams
176•1 into sub-areas, for example, r1, r2, r3 and r4, and each of
the primary electron beams 176•1 is assigned to each of the
sub-areas r1 to r4. Then, the primary electron beams 176•1 are
deflected in the X axis direction at a time by the deflector 176•6
while the wafer W is moved in the Y axis direction to scan the sub-areas
r1 to r4 with the primary electron beams 176•1. In this way, the
area R is scanned with the primary electron beams 176•1.

[1131]Furthermore, the primary optical system of the multi-beam is not
limited to that of FIG. 176, but it is only essential that the beam
should be a multi-beam at the time when it is applied to the sample and,
for example, a single electron gun may be used.

[1132]In the defect inspection apparatus EBI described above, a mechanism
capable of placing the wafer W on a stage and positioning the stage
accurately in a vacuum chamber is preferably used. To accurately position
the stage, for example, a structure in which the stage is supported by a
static-pressure bearing in a non-contact manner is employed. In this
case, in order that high-pressure gas supplied from the static-pressure
bearing is not discharged into the vacuum chamber, it is desirable that a
differential exhaust mechanism discharging high-pressure gas is formed in
the area of the static-pressure bearing to maintain the degree of vacuum
of the vacuum chamber.

[1133]FIG. 178 shows one example of the configuration of a mechanism for
accurately positioning a stage holding the wafer W in a vacuum chamber,
and a circulation piping system of inert gas. In FIG. 178, the leading
end portion of a column 178•1 irradiating primary electrons to the
wafer W, i.e. a primary electron irradiating portion 178•2 is
attached to a housing 178•3 sectioning a vacuum chamber C. The
wafer W placed on a movable table in the X direction (lateral direction
in FIG. 178) of a high-accuracy XY stage 178•4 is placed just below
the column 178•1. By moving the XY stage 178•4 in X and Y
directions (direction perpendicular to sheet face in FIG. 178), primary
electrons can be correctly irradiated with respect to any position on the
surface of the wafer W.

[1134]A seat 178•5 of the XY stage 178•4 is fixed on the
bottom wall of the housing 178•3, and a Y table 178•6 moving
in the Y direction is placed on the seat 178•5. Raised portions are
formed on both side faces of the Y table 178•6 (left and right side
faces in FIG. 178), and the raised portions fit into a pair of recessed
grooves formed on a pair of Y direction guides 178•7a and
178•7b provided on the seat 178•5. The recessed grooves
extend in the Y direction over almost the full lengths of the Y direction
guides 178•7a and 178•7b. Static-pressure bearings (not
shown) each having a well known structure are provided on the upper and
lower faces and the side faces of the raised portions protruding into the
recessed grooves. By blowing high-pressure and high-purity inert gas (N2
gas, Ar gas, etc.) via the static-pressure bearings, the Y table
178•6 is supported on the Y direction guides 178•7a and
178•7b in a non-contact manner, and can make a reciprocating
motion. Furthermore, a linear motor 178•8 having a well known
structure is placed between the seat 178•5 and the Y table
178•6 for driving the Y table 178•6 in the Y direction.

[1135]On the upper side of the Y table 178•6, an X table 178•9
is placed in such a manner that it can move in the X direction. A pair of
X direction guides 3178•10a and 178•10b (only X direction
guide 178•10a is shown in FIG. 178) identical in structure to the Y
direction guides 178•7a and 178•7b for the Y table
178•6 are provided in such a manner as to surround the X table
178•9. Recessed grooves are formed on the sides of the X direction
guides facing the X table 178•9, and raised portions protruding
into the grooves are formed on the side parts of the X table 178•9
facing the X direction guides. These recessed grooves extend over the
full lengths of the X direction guides. Static-pressure bearings (not
shown) similar to the static-pressure bearings for supporting the Y table
178•6 in a non-contact manner are provided on the upper and lower
faces and side faces of the raised portions of the X direction table
178•9 protruding into the recessed grooves. By supplying
high-pressure and high-purity inert gas to the static-pressure bearings
to blow the inert gas from the static-pressure bearings to the guide
surfaces of the X direction guides 178•10a and 178•10b, the X
table 178•9 is accurately supported on the X direction guides
178•10a and 178•10b in a non-contact manner. A linear motor
178•11 having a well known structure is placed on the Y table
178•6 for driving the X table 178•9 in the X direction.

[1136]Since a stage mechanism with static-pressure bearings that is used
in the atmosphere can be directly used as the XY stage 178•4, an XY
stage equivalent in accuracy in to an high-accuracy stage for the
atmosphere for use in a light-exposure apparatus or the like can be
achieved as an XY stage for defect inspection apparatus at almost the
same cost and in almost the same size. Furthermore, the wafer W is not
placed directly on the X table 178•9, but is usually placed on a
sample table having a function of detachably holding the wafer W and
changing the position by a small amount with respect to the XY stage
178•4.

[1137]The inert gas is supplied to the static-pressure bearings through
flexible tubes 178•12 and 178•13 and a gas channel (not
shown) formed in the XY stage 178•4. The high-pressure inert gas
supplied to the static-pressure bearings are blown into gaps of several
microns and several tens of microns formed between the static-pressure
bearings and the opposite guide surfaces of the Y direction guides
178•7a and 1878•7b and the X direction guides 178•10a
and 178•10b to correctly position the Y table 178•6 and the X
table 178•9 in the X direction, Y direction and Z direction
(vertical direction in FIG. 178) with respect to the guide surfaces. Gas
molecules of the inert gas blown from the static-pressure bearings
diffuse into the vacuum chamber C, and are discharged through exhaust
ports 178•14, 178•15a and 178•15b and vacuum tubes
178•16 and 178•17 by a dry vacuum pump 178•18. The seat
178•5 is cut through so that the suction ports of the exhaust ports
178•15a and 178•15b are provided on the upper face of the
seat 178•5. In this way, the suction ports are situated near the
position at which the high-pressure is discharged from the XY stage
178•4, thus preventing the pressure within the vacuum chamber C
from being increased by the high-pressure gas blown from the
static-pressure bearings.

[1138]The exhaust port of the dry vacuum pump 178•18 is connected to
a compressor 178•20 through a tube 178•19, and the exhaust
port of the compressor 178•20 is connected to the flexible tubes
178•12 and 178•13 through tubes 178•21, 178•22,
178•23 and regulators 178•24 and 178•25. Accordingly,
inert gas discharged from the dry vacuum pump 178•18 is compressed
again by the compressor 178•20, adjusted to have an appropriate
pressure by the regulators 178•24 and 178•25, then supplied
again to the static-pressure bearings of the XY table. In this way,
high-purity inert gas is circulated and reused, thus making it possible
to save inert gas, and no inert gas is emitted from the defect inspection
apparatus EBI, thus making it possible to prevent an accident such as
suffocation with inert gas. Furthermore, removal means 178•26 such
as a cold trap or filter is preferably provided at some midpoint in the
tube 178•21 on the discharge side of the compressor 178•20,
so that impurities such as water and oil entering the circulating gas are
trapped and prevented from being supplied to the static-pressure
bearings.

[1139]A differential exhaust mechanism 178•27 is provided around the
leading end portion of the column 178•1, i.e. the primary electron
irradiating portion 178•2. This is intended to keep the pressure of
a primary electron beam irradiation space 178•28 at a sufficiently
low level even if the pressure within the vacuum pump is high. A ring
member 178•29 of the differential exhaust mechanism 178•27
provided around the primary electron irradiating portion 178•2 is
positioned with respect to the housing 178•3 so that a very small
gap of several microns to several tens of microns is formed between the
lower face of the ring member (face opposite to the wafer W) and the
wafer W.

[1140]A ring groove 178•30 is formed in the lower face of the ring
member 178•29, and the ring groove 178•30 is connected to an
exhaust port 178•31. The exhaust port 178•31 is connected to
a turbo-molecular pump 178•33 being an ultra-high vacuum pump
through a vacuum tube 178•32. Furthermore, an exhaust port
178•34 is provided at an appropriate location in the column
178•1, and the air exhaust port 178•34 is connected to a
turbo-molecular pump 178•36 through a vacuum tube 178•35. The
turbo-molecular pumps 178•33 and 178•36 are connected to the
dry vacuum pump 178•18 by vacuum tubes 178•37 and
178•38. Thus, gas molecules of inert gas entering the differential
exhaust mechanism 178•27 and the charged electron beam irradiation
space 178•26 are discharged through the ring groove 178•30,
the exhaust port 178•31 and the vacuum tube 178•32 by the
turbo-molecular pump 178•33, and therefore gas molecules entering
the space 178•28 surrounded by the ring member 178•29 from
the vacuum chamber C. In this way, the pressure within the primary
electron irradiation space 178•28 can be kept at a low level, thus
making it possible to apply primary electrons without any problems.
Furthermore, gas molecules suctioned from the leading end portion of the
column 178•1 are discharged through the air exhaust port
178•34 and the vacuum tube 178•35 by the turbo-molecular pump
178•36. The gas molecules discharged from the turbo-molecular pumps
178•33 and 178•36 are collected by the dry vacuum pump
178•18 and supplied to the compressor 178•20.

[1141]Furthermore, the ring groove 178•30 may have a double or
triple structure depending on the pressure within the vacuum chamber C or
the pressure within the primary electron irradiation space 178•28.
Furthermore, in the inspection apparatus shown in FIG. 178, one dry
vacuum pump is used for the roughing vacuum pump of the turbo-molecular
pump and the pump for evacuating the vacuum chamber, but the chamber may
be evacuated with dry vacuum pumps of different lines depending on the
flow rate of high-pressure gas supplied to the static-pressure bearing of
the XY stage, the volume and inner surface area of the vacuum chamber,
the inner diameter and length of the vacuum tube and the like.

[1142]Dry nitrogen is generally used as high-pressure gas supplied to the
static-pressure bearing of the XY stage 178•4. If possible,
however, inert gas of higher purity is preferably used. This is because
if impurities such as water and oil are contained in the gas, molecules
of theses impurities are deposited on the inner surface of the housing
178•3 sectioning the vacuum chamber C and the surfaces of the stage
components to reduce the degree of vacuum, or deposited on the surface of
the wafer W to reduce the degree of vacuum of the primary electron
irradiation space 178•28. Furthermore, since it is necessary to
prevent the situation in which the gas contains water and oil where
possible, the turbo-molecular pumps 178•33 and 178•36, the
dry vacuum pump 178•18 and the compressor 178•20 are each
required to have a structure such that no water and oil enters the gas
channel.

[1143]Furthermore, as shown in FIG. 178, a high-purity inert gas supply
system is connected to the circulation piping system of inert gas, and
plays a role to fill high-purity inert gas in the vacuum chamber C and
all circulation systems including the vacuum tubes 178•16,
178•15, 178•32, 178•35 and 178•37 and the
pressure tubes 178•19, 178•21, 178•22, 178•23 and
178•39 when circulation of gas is started, and a role to supply an
amount of gas equivalent to a shortfall in case where a flow rate of
circulating gas drops for some cause. Furthermore, by imparting to the
dry vacuum pump 178•18 a function of compression to an atmospheric
pressure or higher, the dry vacuum pump 178•18 can be made to serve
also as the compressor 178•20. Further, instead of the
turbo-molecular pump 178•36, a pump such as an ion pump or getter
pump can be used as an ultra-high vacuum pump for use in evacuation of
the column 178•1. However, if such an entrapment pump is used, a
circulation piping system cannot be built. Instead of the dry vacuum pump
178•18, a different type of dry pump such as diaphragm-type dry
pump may be used.

[1144]FIG. 179 shows examples of values of the sizes of the ring member
178•29 of the differential exhaust mechanism 178•27 and the
ring groove 178•30 formed thereon. Here, double ring grooves
isolated from each other in a radial direction are provided. The flow
rate supplied to the static-pressure bearing is usually about 20 L/min
(equivalent in atmospheric pressure). Provided that the vacuum chamber C
is evacuated with a dry pump having a pumping speed of 20000 L/min
through a vacuum tube having an inner diameter of 50 mm and a length of 2
m, the pressure within the vacuum chamber is about 160 Pa (about 1.2
Torr). At this time, if the sizes of the differential exhaust mechanism
178•27, the ring member 178•29, the ring groove 178•30
and the like are set as shown in FIG. 179, the pressure within a primary
electron irradiation space 56 can be kept at 10-4 Pa (10-6
Torr).

[1145]FIG. 180 schematically shows the overall configuration of an
inspection system having the defect inspection apparatus EBI described
with FIGS. 172 to 179. As shown in the figure, components on the route
ranging from the primary optical system of the defect inspection
apparatus EBI through the wafer W and the secondary optical system to the
detection system D are housed in the column 178•1 exhibiting a
magnetic shield function, and the column 178•1 is placed on the
upper face of a vibration removal table 180•1 supported by an
active vibration removal unit so as to prevent transfer of vibrations
from outside. The inside of the column 178•1 is kept under vacuum
by a vacuum pumping system 180•2. A necessary voltage is supplied
from a control power supply 180•3 through a high-pressure cable
180•4 to components of the primary optical system and the secondary
optical system in the column 178•1.

[1146]An alignment mechanism 180•5 comprising an optical microscope
and auto-focusing means is provided at an appropriate location in the
column 178•1 to place components constituting the primary optical
system and the secondary optical system on predetermined optical axes and
make an adjustment so that primary electrons emitted from the electron
gun automatically come into a focus on the wafer W.

[1147]The XY stage 178•4 comprising a chuck (not shown) for placing
and fixing the wafer W is provided on the upper face of the vibration
table 180•1, and the position of the XY stage 178•4 during a
scan period is detected at predetermined intervals by a laser
interferometer. Further, a loader 180•6 for accumulating a
plurality of wafers W as inspected objects, and a transportation robot
180•7 for holding the wafer in the loader 180•6 and placing
the wafer W on the XY stage 178•4 in the column 178•1, and
taking the wafer W from the column 178•1 after inspection are
placed on the upper face of the vibration removal table 180•1.

[1148]The operation of the overall system is controlled by a main
controller 180•8 in which necessary programs are installed. The
main controller 180•8 comprises a display 180•9, and is
connected to the detection system D through a cable 180•10.
Consequently, the main controller 180•8 can receive a digital image
signal from the detection system D through the cable 180•10 to
process the signal with the image processing unit 172•10, and
display the contents of an inspection result file obtained by the
scanning of the wafer W, a defect distribution of the wafer W and the
like on the display 180•9. Furthermore, the main controller
180•8 displays an operation state of the system on the display
180•9 to control the operation of the overall system.

[1149]Furthermore, in the above description, the stage holding the wafer W
is movable in the XY plane, but in addition thereto, the stage may be
rotatable about any axis perpendicular to the XY plane or extending
passing the XY plane. Furthermore, the inspection object is not limited
to a wafer, but any sample capable of being inspected with an electron
beam, such as a mask, is included as an inspected object. Further, by
mutually connecting the projection-type electron beam apparatus in this
embodiment, a beam scanning defect review apparatus, a server and the
main controller through a LAN, a distributed defect inspection network
can be built.

[1150]As apparent from the above description, this embodiment exhibits the
following remarkable effects.

(1) Because the sample is irradiated with a plane beam, throughput can be
improved to the extent that for example, defect inspection time per wafer
can be reduced by a factor of 7 compared to the conventional beam
scanning inspection apparatus.(2) A space charge effect can be avoided
because it is not necessary to focus primary electrons on a beam spot,
and the sample is not significantly damaged because the sample is
irradiated in a low current density.(3) Because the sample is irradiated
with a plane beam, inspection can be performed for a size smaller than
one pixel.(4) By selecting an accelerating voltage of the electron gun
and a voltage applied to the sample, and adjusting an objective lens, the
apparatus can be operated in any one of a positive charge mode, a
negative charge mode and a reflection electron imaging mode, thus making
it possible to perform appropriate inspection according to the inspection
site in the sample.(5) By using an electrostatic lens, the primary
optical system and/or the secondary optical system can be downsized and
improved in accuracy.